Here I present recolored Laser and Plasma Bullet and Hit sprites, now finally working.
Plasma Bullet and Hit sprites:
Red
Blue
Purple
Laser Bullet and Hit sprites (small, medium and large version for each color):
Red
Green
Blue
Purple
Including sample ruleset which has to be adjusted to your weapon of choice.
As the latest nightly Build now allows BulletSprite to be a function of ammo, you can create several ammo types for one weapon which have different bullet colors.
See attached TestGun Mod and testing savegame for a real life demonstration of that, but keep in mind that this gun is for testing purposes only - it will barely do any damage so you can shoot the aliens in all the colors you want.