No, not very hard, tell me the colors for each led and each strip.
There is a color reference here : Pixel reference · FastLED/FastLED Wiki · GitHub
In this version of the code, the button handling is minimal. This means that you're supposed to push and release quickly, never keep the button pushed. Is it ok for you or would you need some better button handling, such as waiting for the button to be released to increment the leds?