I've got a girl who has bright red lipstick just like what you've described. She's a light/cream body with dark red/purple fins, and speckles all over her head...and her lipstick. ;) The lipstick is actually why I bought her...she was so tiny, and that perfect dark-red fishy pout... ;)
I've had others who started off with that light coloring, and as they aged, got better food, had better water conditions, their colors changed and became much more vibrant. I've also noticed that many of mine who started out with butterfly translucency on the edges of their fins eventually came to have their color extending in streaks into the translucence after a few months. (it was *not* septicemia, which had me freaked out for awhile! ;)
As long as he's acting happy and he's not swollen, I vote for it just being his coloring. My understanding is that when they get dropsy, it's very evident that there is something very wrong. I've only had one fish who had it, a girl who was still in QT, and she swelled up (entire body), started breathing heavily, refused food, etc. You could tell she was sick.