Assuming you are not rewriting the palette scanline-by-scanline...
Amiga is stuck with 16 colors for the whole bitmap screen unless extra-halfbrite mode is used, then it goes up to 32 colors (extra colors must be half as bright as the base colors). Using the hardware sprites (3 colors + transparent) can add up to 12 more colors.
Meanwhile on the SNES, the most-used video mode has two background layers with 15-color tiles (plus transparent), and one background layer with 3-color tiles (plus transparent). 8 different palettes can be selected, for 128 colors.
Then there are sprites too, lots of sprites can be on the screen at once. 15-colors (plus transparent) for a sprite, and 8 different palettes can be selected.
Then afterwards, color math can be applied, you can make graphics use additive blending (light effects), subtractive blending (darkness effects), or 50% transparent blending.