hi, Blackwork tends to fade if you are always in the sun, but solid bold black tattoos will keep their look better over time.Really all depends on the skill of the artist and quality of ink too.
you can always get them re-done again and again. one of my tats ive had for 9 years and with the sun exposure i used to get everday (i was a beach bum) its ready for a little touch up.
I've heard that green can fade a little more than other colours. But as someone else said, you can get them touched up and its a pretty quick process.
My dad has an eagle with some awesome design of greenery under it and the green faded to almost invisible because he used to CONSTANTLY be out in the sun. The purple ink that was used to write his name turned that ugly faded tattoo green-y color.
I've never been fond of color tattoos anyway. I like solid black ones. I was wondering the same thing tho! I'd think black ones would be easier to touch up if needed, since you won't have to try to match the color like you would with other colors.