PLAYPAL
From DoomWiki.org
A PLAYPAL is really a collection of palettes used for various purposes. It has a total of fourteen palettes of 768 bytes. Each palette has 256 colors of three unsigned bytes each (0-255); one for each of red, green and blue. Furthermore, the COLORMAP resource also affects the display of colors on screen.
The palettes each have a specific function:
0: normal
1: unknown
2-8: progressively more red (8 is most red). Used to show pain when the player is hurt, and reddens the screen when the player picks up a berserk pack.
9: unknown
10-12: progressively more white. Used very briefly as the player picks up items.
13: green tint, used when the radiation suit is being worn
This information is from the Unofficial Doom Specs.