Well, I assumed the reason for the pink or purple (or, more correctly, magenta; and since I've also heard here about white) was simply the result of "sequencing" the input(s) to the LED, thereby giving the "appearance" of a different color. In the case of RGB LEDs, blue gives blue, red gives red, and green gives green. But, when you sequence two or more of these input signals (at 25 ms, or faster), the naked eye "sees" yellow, cyan, magenta, or white.
So, since we know what red means, and we know what blue means... Well, there ya' go.