PPU palettes

The NES has a limited selection of color outputs. A 6-bit value in the palette memory area corresponds to one of 64 outputs. The emphasis bits of the PPUMASK register ($2001) provide an additional color modifier.

For more information on how the colors are generated on an NTSC NES, see: NTSC video

Memory Map

The palette for the background runs from VRAM $3F00 to $3F0F; the palette for the sprites runs from $3F10 to $3F1F. Each color takes up one byte.

Address	Purpose
$3F00	Universal background color
$3F01-$3F03	Background palette 0
$3F05-$3F07	Background palette 1
$3F09-$3F0B	Background palette 2
$3F0D-$3F0F	Background palette 3
$3F11-$3F13	Sprite palette 0
$3F15-$3F17	Sprite palette 1
$3F19-$3F1B	Sprite palette 2
$3F1D-$3F1F	Sprite palette 3

Each palette has three colors. Each 16x16 pixel area of the background can use the backdrop color and the three colors from one of the four background palettes. The choice of palette for each 16x16 pixel area is controlled by bits in the attribute table at the end of each nametable. Each sprite can use the three colors from one of the sprite palettes. The choice of palette is in attribute 2 of each sprite (see PPU OAM).

Addresses $3F04/$3F08/$3F0C can contain unique data, though these values are not used by the PPU when normally rendering (since the pattern values that would otherwise select those cells select the backdrop color instead). They can still be shown using the background palette hack, explained below.

Addresses $3F10/$3F14/$3F18/$3F1C are mirrors of $3F00/$3F04/$3F08/$3F0C. Note that this goes for writing as well as reading. A symptom of not having implemented this correctly in an emulator is the sky being black in Super Mario Bros., which writes the backdrop color through $3F10.

Thus, indices into the palette are formed as follows:

43210
|||||
|||++- Pixel value from tile data
|++--- Palette number from attribute table or OAM
+----- Background/Sprite select

As in some second-generation game consoles, values in the NES palette are based on hue and brightness:

76543210
||||||||
||||++++- Hue (phase, determines NTSC/PAL chroma)
||++----- Value (voltage, determines NTSC/PAL luma)
++------- Unimplemented, reads back as 0

Hue $0 is light gray, $1-$C are blue to red to green to cyan, $D is dark gray, and $E-$F are mirrors of $1D (black). The canonical code for "black" is $0F or $1D. $0D should not be used; it results in a "blacker than black" signal that may cause problems for some TVs. It works this way because of the way colors are represented in an NTSC or PAL signal, with the phase of a color subcarrier controlling the hue. For details, see NTSC video, or for a list see Color $0D games.

The 2C03 RGB PPU used in the PlayChoice-10 and Famicom Titler renders hue $D as black, not dark gray. The 2C04 PPUs used in many Vs. System arcade games have completely different palettes as a copy protection measure.

Palettes

2C02

NES palette generated with Bisqwit's tool

The RF Famicom, AV Famicom, NES (both front- and top-loading), and the North American version of the Sharp Nintendo TV use the 2C02 PPU. Unlike some other consoles' video circuits, the 2C02 does not generate RGB video and then encode that to composite. Instead it generates NTSC video directly in the composite domain. The TV decodes this into RGB to drive its picture tube, and most TVs' decoders intentionally deviate somewhat from the NTSC standard.

Some emulators decode the NTSC signal in real time. Others use a predefined palette, such as one commonly stored in Classic VGA Palette format (.pal), in which each triplet represents the sRGB color that results from decoding a large flat area with a given palette value. Using such a table directly will result in overly "clean" video that looks somewhat more like a PlayChoice (see 2C03 below), and some games will look graphically sterile if quirks of the NES's video output are not emulated. However, sometimes people want something functional before they bother with actually generating a composite signal and decoding it, or they're making an emulator for a low-end device that cannot decode NTSC video in real time.

The following table was generated using blargg's Full Palette demo on Nestopia:

 84  84  84    0  30 116    8  16 144   48   0 136   68   0 100   92   0  48   84   4   0   60  24   0   32  42   0    8  58   0    0  64   0    0  60   0    0  50  60    0   0   0
152 150 152    8  76 196   48  50 236   92  30 228  136  20 176  160  20 100  152  34  32  120  60   0   84  90   0   40 114   0    8 124   0    0 118  40    0 102 120    0   0   0
236 238 236   76 154 236  120 124 236  176  98 236  228  84 236  236  88 180  236 106 100  212 136  32  160 170   0  116 196   0   76 208  32   56 204 108   56 180 204   60  60  60
236 238 236  168 204 236  188 188 236  212 178 236  236 174 236  236 174 212  236 180 176  228 196 144  204 210 120  180 222 120  168 226 144  152 226 180  160 214 228  160 162 160

Other tools for generating a palette include one by Bisqwit and one by Drag. These simulate generating a large area of one flat color and then decoding that with the adjustment knobs set to various settings.

The 2C03, 2C04, and 2C05, on the other hand, all output analog red, green, blue, and sync (RGBS) signals. The sync signal contains horizontal and vertical sync pulses in the same format as an all-black composite signal. Each of the three video channels uses a 3-bit DAC driven by a look-up table in a 64x9-bit ROM inside the PPU. The look-up tables (one digit for each of red, green, and blue, in order) are given below:

2C03 and 2C05

This palette is intentionally similar to the NES's standard palette, but notably is missing the greys in entries $2D and $3D. The 2C03 is used in Vs. Duck Hunt, Vs. Tennis, all PlayChoice games, the Famicom Titler, and the Famicom TV. The 2C05 is used in some later Vs. games as a copy protection measure. Both have been used in RGB mods for the NES, as a circuit implementing A0' = A0 xor (A1 nor A2) can swap PPUCTRL and PPUMASK to make a 2C05 behave as a 2C03.

333,014,006,326,403,503,510,420,320,120,031,040,022,000,000,000
555,036,027,407,507,704,700,630,430,140,040,053,044,000,000,000
777,357,447,637,707,737,740,750,660,360,070,276,077,000,000,000
777,567,657,757,747,755,764,772,773,572,473,276,467,000,000,000

0x00	0x01	0x02	0x03	0x04	0x05	0x06	0x07	0x08	0x09	0x0A	0x0B	0x0C	0x0D	0x0E	0x0F
0x10	0x11	0x12	0x13	0x14	0x15	0x16	0x17	0x18	0x19	0x1A	0x1B	0x1C	0x1D	0x1E	0x1F
0x20	0x21	0x22	0x23	0x24	0x25	0x26	0x27	0x28	0x29	0x2A	0x2B	0x2C	0x2D	0x2E	0x2F
0x30	0x31	0x32	0x33	0x34	0x35	0x36	0x37	0x38	0x39	0x3A	0x3B	0x3C	0x3D	0x3E	0x3F

Kevtris's dumped palettes imply that the monochrome bit has unique function on the 2C03 and 2C05: instead of just using the leftmost column of the palette (and forcing the lower four bits to zero), instead the top two bits index into a palette with colors: 000, 333, 777, 777. Given that the 2C04 does not do this, this exception feels weird, and corroboration would be appreciated.

RC2C03B

For no particularly discernible reason, the palette for this specific PPU varies in six colors:

333,014,006,326,403,503,510,420,320,100,031,040,022,000,000,000
555,016,027,407,507,704,700,630,430,140,040,053,044,000,000,000
777,357,447,637,707,717,740,750,660,340,070,276,077,000,000,000
777,547,657,757,747,755,764,772,773,552,473,276,467,000,000,000

0x00	0x01	0x02	0x03	0x04	0x05	0x06	0x07	0x08	0x09	0x0a	0x0b	0x0c	0x0d	0x0e	0x0f
0x10	0x11	0x12	0x13	0x14	0x15	0x16	0x17	0x18	0x19	0x1a	0x1b	0x1c	0x1d	0x1e	0x1f
0x20	0x21	0x22	0x23	0x24	0x25	0x26	0x27	0x28	0x29	0x2a	0x2b	0x2c	0x2d	0x2e	0x2f
0x30	0x31	0x32	0x33	0x34	0x35	0x36	0x37	0x38	0x39	0x3a	0x3b	0x3c	0x3d	0x3e	0x3f

The pattern compared to the normal 2C03 is that where color bits 0-1 are 01, green is ANDed with 5 (bit 1 is 0). No games are known to be designed for this palette. Given the pattern, it was probably a mistake in the mask.

2C04

All four 2C04 PPUs contain the same master palette, but in different permutations. It's almost a superset of the 2C03/5 palette, adding four greys, six other colors, and making the bright yellow more pure.

No version of the 2C04 was ever made with the below ordering, but it shows the similarity to the 2C03:

333	014	006	326	403	503	510	420	320	120	031	dup of ↙	022	111	003	020
555	036	027	407	507	704	700	630	430	140	040	053	044	222	200	310
777	357	447	637	707	737	740	750	660	360	070	dup of ↓	077	444	000	000
777	567	657	757	747	755	764	770	773	572	473	276	467	666	653	760

The PPUMASK monochrome bit has the same implementation as on the 2C02, and so it has an unintuitive effect on the 2C04 CPUs. Rather than forcing colors to grayscale, it instead forces them to the first column.

RP2C04-0001

MAME's source claims that Baseball, Freedom Force, Gradius, Hogan's Alley, Mach Rider, Pinball, and Platoon require this palette.

755,637,700,447,044,120,222,704,777,333,750,503,403,660,320,777
357,653,310,360,467,657,764,027,760,276,000,200,666,444,707,014
003,567,757,070,077,022,053,507,000,420,747,510,407,006,740,000
000,140,555,031,572,326,770,630,020,036,040,111,773,737,430,473

RP2C04-0002

MAME's source claims that Castlevania, Mach Rider (Endurance Course), Raid on Bungeling Bay, Slalom, Soccer, Stroke & Match Golf (both versions), and Wrecking Crew require this palette.

000,750,430,572,473,737,044,567,700,407,773,747,777,637,467,040
020,357,510,666,053,360,200,447,222,707,003,276,657,320,000,326
403,764,740,757,036,310,555,006,507,760,333,120,027,000,660,777
653,111,070,630,022,014,704,140,000,077,420,770,755,503,031,444

RP2C04-0003

MAME's source claims that Balloon Fight, Dr. Mario, Excitebike (US), Goonies, and Soccer require this palette.

507,737,473,555,040,777,567,120,014,000,764,320,704,666,653,467
447,044,503,027,140,430,630,053,333,326,000,006,700,510,747,755
637,020,003,770,111,750,740,777,360,403,357,707,036,444,000,310
077,200,572,757,420,070,660,222,031,000,657,773,407,276,760,022

RP2C04-0004

MAME's source claims that Clu Clu Land, Excitebike (Japan), Ice Climber (both versions), and Super Mario Bros. require this palette.

430,326,044,660,000,755,014,630,555,310,070,003,764,770,040,572
737,200,027,747,000,222,510,740,653,053,447,140,403,000,473,357
503,031,420,006,407,507,333,704,022,666,036,020,111,773,444,707
757,777,320,700,760,276,777,467,000,750,637,567,360,657,077,120

Backdrop color (palette index 0) uses

During forced blanking, when neither background nor sprites are enabled in PPUMASK ($2001), the picture will show the backdrop color. If only the background or sprites are disabled, or if the left 8 pixels are clipped off, the PPU continues its normal video memory access pattern but uses the backdrop color for anything disabled.

The background palette hack

If the current VRAM address points in the range $3F00-$3FFF during forced blanking, the color indicated by this palette location will be shown on screen instead of the backdrop color. (Looking at the relevant circuitry in Visual 2C02, this is an intentional feature of the PPU and not merely a side effect of how rendering works.) This can be used to display colors from the normally unused $3F04/$3F08/$3F0C palette locations. A loop that fills the palette will cause each color in turn to be shown on the screen, so to avoid horizontal rainbow bar glitches while loading the palette, wait for a real vertical blank first using an NMI technique.

Color names

When programmers and artists are communicating, it's often useful to have human-readable names for colors. Many graphic designers who have done web or game work will be familiar with HTML color names.

Luma

$0F: Black
$00: Dark gray
$10: Light gray or silver
$20: White
$01-$0C: Dark colors, medium mixed with black
$11-$1C: Medium colors, similar brightness to dark gray
$21-$2C: Light colors, similar brightness to light gray
$31-$3C: Pale colors, light mixed with white

Chroma

Names for hues:

$x0: Gray
$x2: Blue
$x4: Magenta
$x6: Red
$x7: Orange
$x8: Yellow or olive
$xA: Green
$xC: Cyan

RGBI

These NES colors approximate colors in 16-color RGBI palettes, such as the CGA, EGA, or classic Windows palette, though the NES doesn't really have a good yellow:

$02: Navy
$06: Maroon
$12: Blue
$14: Purple
$16: Red
$17: Brown
$18: Olive
$1A: Green
$1C: Aqua
$24: Fuchsia/Magenta
$2A: Lime
$2C: Teal

PPU palettes

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