size(400,200);
color clr = 255, clr2 = color(255,255,255);
noStroke();
fill(red(clr),green(clr),blue(clr));
rect(0,0,200,200);
fill(red(clr2),green(clr2),blue(clr2));
rect(200,0,200,200);
I know color is stored as a weird integer (like -1 for white). But it should at least work the same way as fill(255);