The SLCD board has an 80KB frame buffer. This provides for 8-bit per-pixel color at 320 x 240 resolution. In order to support a consistent color image with multiple on-screen bitmaps, a constant color palette is used. The palette maps the 8-bit pixel index to the 12-bit color value sent to the panel.
The palette provides 16 gray scales (including black and white) and 6 color values for each of red, green, and blue. This totals 6*6*6*16 = 231 colors (actually only 230 because of black redundancy).
In 24-bit RGB terms, the colors supported are as follows:
R, G, B = independently either 0x00, 0x33, 0x66, 0x99, 0xCC or 0xFF (six colors)
R=G=B = 0x00, 0x11, 0x22, …0xEE, 0xFF (16 grays).
A file ps8666.act is provided that contains the Adobe Photoshop palette corresponding to this color mapping.