Do you think that all of us perceive colors the same way? I mean, what if what I consider to be blue is red to someone else. Or maybe other people see colors that I cannot even comprehend. After all, it's all relative.
When you're young, someone tells you the sky is blue and the grass is green. You say, "Sure, whatever", and continue to suck down the remainder of your Fla-Vor-Ice, then roll up the plastic packaging and blow, like one of those party favors, not considering that everyone's perception of color could be vastly different. I mean, everyone's physiology differs, right? What's to say that subtle differences in people's rod and cones could result in something like this? Just something to think about.