In the additive colors game (PrimaryColors) you use color lights to turn a black stage white. In the subtractive colors game you use color pigments to turn a white canvas black. If that is a similarity, it is the only one.
PrimaryColors II is more difficult. It is not based on Tetris model. It is two dimensional. It does not have an obvious strategy. Also, it has a maximum possible score, which, when you reach it, you will know for sure that you have arrived. This version is the first release on CNET Download.com.