With a little more testing, I decided to remove that part of the game and make it simpler to understand.
I just changed the “color war” modifier so that colour changing is twice as effective as it was and now there is no confusion about having to keep grabbing even once the whole block is on your side. It makes the game slightly easier to play, but much easier to understand.
Sometimes when you make something you become attached to a way it was, and attached to the original idea you had about a cool feature. When that feature doesn’t work as well as intended it can be hard to give it up. In this case I managed to.