Red fades to pink in stressed rummynoses (when they are introduced into a new tank).
"This is a distinctive looking little tetra with black and white "checkerboard" markings on its tail and a bright red nose, for which it is named. The red nose is actually the best indication of the fish's health and well-being--when it is feeling ill at ease or not in tiptop shape (for example, when first introduced to the tank), this red will fade to a dull pink, barely distinguishable from its unremarkable gray body color. "