PaulS:
Where do you initialize a, r, g, and b in setup? I don't see that happening.
Maybe I'm unclear on what initialize means. I thought clear()—which sets every value in the array to 0—would be considered initializing it. Wouldn't I just have to use a loop similar for loop to initialize the arrays?
PaulS:
Yes, but, then they would be local to setup() where they are not used, rather than local to loop, where they are used.
This makes sense, but if I declare them in loop then won't they will be declared again every frame? Should I be declaring them at the beginning of loop() and then have a separate looping function inside of loop() (so that loop() essentially only runs once)? I'm getting a little off topic here, I should probably spend some more time tinkering before asking so many questions.