Distinguishing blue from green in language
The English language makes a distinction between blue and green, but some languages do not. Of these, quite a number, mostly in Africa, do not distinguish blue from black either, while there are a handful of languages that do not distinguish blue from black but have a separate term for green. Also, some languages treat light (often greenish) blue and dark blue as separate colors, rather than different variations of blue, while English does not. (via sleevia)
This was told as one of the facts supporting Sapir-Whorf hypothesis. I once attended a seminar where perception speed of different colors were shown to be related with language having the color name. Turkish, by the way, is one of those languages separating shades of blue.