The article's method contrasts colors based on the numerical separation of their RGB values. Unfortunately, human color perception doesn't necessarily follow this model. There are some color pairs that would be judged very far apart by this method, but that a human won't necessarily perceive as contrasting.<p>Also, there's the issue of size. Medium-sized adjacent objects are perceived as having more contrast than large or small ones:<p><a href="http://en.wikipedia.org/wiki/Contrast_(vision)#Contrast_sensitivity" rel="nofollow">http://en.wikipedia.org/wiki/Contrast_(vision)#Contrast_sens...</a><p>So this is a more complex problem than simply choosing colors by number.