I know of males who dye there hair. the reason why more dont is because they tend to keep it short thus it's more maintenance.
I remember it coming up twice whether hair dye was masculine or feminine.
First time was when I was 16 I'd dyed my hair bright blue and to do this I'd of course bleached it. and while in town with a classmate (not really a friend) I pointed out the hair bleach I'd used.
"Ooh you can't use that it's a womans hairdye!" Eh? what do you suggest I use then?
"There are male hair-dyes out there!" Oh hurray Just-for-men with it's large selection of colours dark brown to tea stain brown, and there new colour washed out mouse brown.
She fell silent.

The other time was abit later when I was 17 and working in a supermarket a co-worker had brought some hair bleach I saw him with it and asked what it was and he showed me, we joked "Ahh be careful with that it will make you look like the girl on the front of the packet" and he mentioned how his girlfriend was saying how it was unmanly to dye his hair he didn't give a crap.