It's just a reduced true-color palette, with only 3 bits per component.
QUOTE (Marrr @ Aug 6 2010, 04:33 PM)
my reason for asking is that the sonic games (and a few others) implemented a 'fade' using blue/cyan rather than just decreasing the luminance of each colour.
The purpose of that is making the fading sequence smoother. If all components were reduced/increased together, the whole fading sequence would have only 8 steps (with 3 bits you can only represent 8 values). To make it longer, different color components are modified at different times/rates.
Some Master System games do the same thing (not Sonic games though), and they really benefit from that since that system has only 64 colors. A good example is Daffy Duck In Hollywood
. The Game Gear doesn't need this, having 4096 colors and all.
several magazines (even retro gamer recent) had commented on the genesis having a 'grittier' colour palette than the snes.
The SNES not only can show more colors than than the MD at any given time, but it also has a bigger palette to pick colors from, so it can get away with fading by modifying only the luminance.