palette (t.a.g.)

There was a thing with 8-bit consoles and 16-bit machines: you wouldn't have the bandwidth to select precise color for each individual pixel. The digital-to-analog circuitry that provides signal to your screen might have 5- or 6-bit resolution, you're still stuck to 4 or 8 bits per pixel instead of the 15 (or 18) you should be allowed to use.

The solution was to let you select a subset (usually 16, 256 if you were lucky) of the possible colors you could use at once (per screen or per-object if you were lucky) and have a fast 'palette' memory in addition to the large 'video' memory.

It was a significant artistic constraint, but it allowed tricks like palette cycling animation, fade-in/fade out by palette edition alone and of course palette-swapping to provide more visually unique content with the same video contents.

Of course, pixel artists will speak about 'palettes' when they speak of the restricted set of colours they're using for one particular piece. I'd rather use the tag 'colours' for that purpose.