Dudes in ancient Rome were putting bird shit in their hair to make them appear older and by association more wise. I don't think it's unmanly, but I spend a better part of my day trying to keep bird poop away from me. Also hair dye. Except when I was a teenager in a punk band I had blue hair. I agree with what you say about the integrated man as long as it doesn't include wearing pink socks.
Highlites would be girly...
I think it depends on why you're doing it. When my hair was thinning at top, I used colour (my own natural medium brown) to thicken it. I'm not sure what I think about completely changing your colour, though, unless perhaps you've gone salt-and-pepper and it's just not working. In that case, going one or the other should be fine.
i'm 25 almost never colored my hair at all and going grey i don't see a reason to color my hair
Something simpler - pigmented hair product. I'm a stage actor with salt'n pepper hair, and when I'm called on to play a younger guy, I use one of two products, both of which I found in the "ethnic section" at a Walgreen's. Softee's is a deep-brown hair gel, and Murray's Bees Wax comes clear or black.
Day to day I don't bother.
I don't know if darkening your hair a bit is unmanly. But frosting it is. When I talk to a guy with frosted hair or highlights, I assume he's wearing a panty liner as well.
You grew it Man. Do what you want with it.
If you have it done correctly I imagine no one know, and who would care anyway? To me it's just putting of the inevitable. Most of us are going to go grey, and typically those with black hair (like me) or red hair are going to be the first to see the change b/c the change is contrasting.
The couple who cuts my hair (either him or her depending on who has my appointment) both told me that my gray was coming in fast, but only said that. Then, one day out of the blue he told me to grow a circle beard to see what would come. Actually came out more black than white and looked really good. Following that major lifestyle change he cut my hair really short...really short...and the combination looked really good...what he was trying to do I later found out was balancing the hair and facial growth so that the transition wasn't so obvious....the combination black/grey diverted the focus on my head, and then the short hair made up top less obvious. A very long way to tell you that there may be more ways to deal with wiry grey hair than coloring it. Remember it's still wiry anyway you work with it.