Divert background color choosing in p5js

I'm a noobie, so please be kind to me :)

I'm putting together a p5js script. Background color is random, choosing from an array with values for black or white background. Drawing color is also random.

It works fine most of the times, but from now and then I get a color that can't really be appreciated from the background, so the question is, is there a way in which I can vary the background resulting color depending on the color of the draw? How would I go about discerning what combination is "perceivable" and which one isn't?