fade_from - Gradually fades the palette between two others. Allegro game
programming library.
#include <allegro.h>
void fade_from(const PALETTE source, const PALETTE dest, int
speed);
Fades gradually from the source palette to the dest palette. The speed is from 1
(the slowest) up to 64 (instantaneous).
Note that this function will block your game while the fade is in
effect, and it won't work right visually if you are not in an 8 bit color
depth resolution.
fade_in(3), fade_out(3), fade_interpolate(3),
fade_from_range(3)