Often when you can't find a bug it's because you've assumed something that is not, in fact, true. This is an excellent example. The author assumed he could see a red car on a green terrain. This is one reason pair programming, code reviews, or even just leaving and coming back to your own work can do wonders. People don't always make the same assumptions. In this case, another programmer who wasn't colorblind would have been able to point straight at the box.

It's much more common than one might suspect. "Red-green color blindness affects up to 8% of males of Northern European descent." [wikipedia]

This seems like a stupid mistake to make for someone who has colorblindness, especially after all the troubleshooting.

I do realize that's the point of the story, but I think it's a pretty pointless post. Just like this one I suppose...

TLDR instead of reading the post: code isn't always the problem, people can be stupid.