Actually it feels more like a sudden involuntary loss of sense more than anything. If it's a really bad one, I lose touch with my self completely and collapse physically and mentally (the correct term would be fainting). I'm orthostatic intolerant so I get them very frequently and have been for most of my life.
The rainbow in itself is just light refraction; nothing too spectacular after you see quite a few. If you want to get into religion, they have the rainbow as symbolism among the different branches of religion.
Not knowing how something works and not knowing the function of an object are two different things. You know how Windows works to bring an environment to run applications, but you do not know exactly how it does this.