"They'll sell you thousands of greens. Veronese green and emerald green and cadmium green and any sort of green you like; but that particular green...never!"
-Pablo Picasso
It's slightly comforting to know that even Picasso had problems finding the right paint colour like the rest of us.
as a painter, i can relate. i can never get the correct shade of green, i usually end up settleing because i'm tired of mixing and mixing and never having the desired result.