Since you're feeling experimental, I really recommend that you try the more extreme ends of the spectrum; mild changes often look a bit puzzling and tentative on men ("Is he trying to cover grey? Or look like [insert celebrity name]? Why?"). I'd say strip it out to platinum blond, make a circuit through some intense colours(s), finish with black, and ...plan on buzzing or shaving your head at the end of the summer
Truly temporay hair colour (level 1, it'll say on the box) can only enhance intensity or make your hair a little darker; you cannot lighten your hair with it. If you use it, plan on breaking out the darker coloured pillowcases and towels; it comes off constantly.
"Temporary" (level 2) colour is NOT temporary (the change it will make is so small that it grows out very naturally; but it's there for good, though reds may fade), and may be able to lighten your hair a shade or so, but not enough to look any different than it probbaly does in the summer.
Level 3 is the hardcore stuff. Fun.
Doing it yourself is fine, but put petrolatum along your hairline, over your ears, and anyplace else you do not want to have colour, or you'll have some peculiar looking blotches for several days.