The first thing that comes to mind might not be tweaking the rules exactly, but the color combinations are hard to internalize. Having the result of the combinations be easy to understand quickly would help. This could be from a rule change, or maybe even just how it’s presented. I’m not sure.
There’s an interesting mechanic in there, and the instructions made it very clear. It was a bit easy to setup a few turrets and win the game, but with more exploration, this could be a great twist on tower defense.