Change game icon .pngs to different base colors for my mod.

I need help changing my game icons from their current .pngs to different base colors that fit my mod better. This job consists of changing more than 7 game icons. I have a general theme in mind, but I'm open to suggestions regarding how to bring this theme to life. The modified icons are intended for commercial use. If you are familiar with the Factorio game, I will be changing the entity, icon, and technology pngs of the assembler-mk-2. Instead of the blue, I want improved to be dark green, the advanced to be red, the elite to be silver, and the super to be gold.