Here is the full list of all 22 ChromaGun achievements.
Get killed by a WorkerDroid.
Fire 100 shots.
Mix a color. It's not that hard, really.
Finish Chapter 1.
Open a door by activating a trigger.
Shoot a WorkerDroid.
Find the hidden cake we actually have, as opposed to that other game that doesn't have a cake.
Try painting a brown WokerDroid and realize how pointless that was.
Grill a WorkerDroid on a Deadly Electrified Maintenance Tile.
Grill 100 WorkerDroids on Deadly Maintenance Tiles.
Finish Chapter 2.
Finish Chapter 3.
Finish Chapter 4.
Finish Chapter 5.
Finish Chapter 6.
Finish Chapter 7.
Finish Chapter 8.
Solve a chamber in chapter 7 without firing a single shot.
Try jumping... and fail.
Try jumping over a Deadly Electrified Maintenance Tile... and fail horribly.
Simply walk onto the Deadly Electrified Maintenance tile in Chamber 3-1.
Rescue the WorkerDroid in Chamber 5-2.