For those unaware, NES backgrounds can only display 13 colors at a time (without coding tricks like updating palettes mid-scanline) There is one universal background color and four subpalettes of three additional colors each. When I decided to go with chew toys, as the visual theme for the blocks, I wanted to make the game as colorful as possible.
The chew toys come in four different colors, but only use two subpalettes. This is achieved by using hue ramps within the palettes:
So, black is the universal color and the cool subpalette has a dark violet, medium blue, and light teal while the warm subpalette has a light yellow, medium red-orange, and dark red-violet.
To unify the remainder of the game visually, the quote screens and title screen are all constructed using those same two subpalettes:
