Answer:
Could you be growing hair there? If you haven't already, that could be it. Or, you could have a blackhead problem that makes it appear darker in color. Then again, it could just be a discoloration of the skin there. I wouldn't think it'd be any big deal, though.
if you wear black under armour all the time then thats the problem. This used to happen to me. Either that or scrub harder.
your deodorant might be causing an allergic reaction. try a different deodorant, and if there's still a shady color there, go to a dermatologist
I don't know anyone who cares about arm pits. Just won't happen. Your obsessing.
it could be because you sweat too much if thats the case their are certain deoderants to reduce sweat
My cousin had the same proble.
After you shower, use a liquid pore cleanser that girls use.
Don't be embaressed! Pour it on a cotton ball or tissue, then scrub the tissue over your pits.