I know you aren't a hater of any animal just because of their color, I just meant you should be careful about the color comment and rat forums. Many rat people are especially sensitive about the pink-eyed whites being seen as lowly feeders. Your first post would have been taken the wrong way immediately if you were posting in say, the goosemoose rat forum (hint hint on good place for rat advice). You'd have been eaten alive.

As for gender, no big deal either way. Females get along with other females as often as males get along with other males. The rare male will be a fighter in its teenage years and be just asking for a neutering, but usually they are fine. Its always best to find two that are already buddies or to find a rather young one to introduce to an older one. Males tend to grow larger and be lazier and snuggle more, but that only comes with age. My 5 males defy all of those stereotypes, except the getting larger part. None of mine are over 400 grams though. You bet those picture of large "squishy" man rats on forums make me cringe.