Comment by BrenBarn

> If in a langauge there is one word for 2 different colors, speakers of it are unable to see the difference between the colors.

That is quite untrue. It is true that people may be slightly slower or less accurate in distinguishing colors that are within a labeled category than those that cross a category boundary, but that's far from saying they can't perceive the difference at all. The latter would imply that, for instance, English speakers cannot distinguish shades of blue or green.