After coming across this thread on Twitter a while back I learned something really interesting about Galaxian hardware. It turns out the RGB decoder used in Galaxian (and other early Namco color games like Bomb Bee) is capable of a whopping 256 colors, most of which are never used in Galaxian itself. Some additional colors appear in the star generator, but the sprite and tile data is limited to eight shared palettes of four colors each.
Here's a table of possible colors taken from the startup sequence of Bomb Bee and labeled in a hex grid:
Galaxian hardware was used by a huge amount of early arcade games, everything from similar spaceship games like Moon Cresta to a wide variety of bootleg backports, and the hardware served as the foundation for a wide variety of games moving forward, like Frogger and Pac-Man, which were designed for hardware that essentially expanded on the original Galaxian hardware design.