As sill as this may seem, my guild is having a wonderfull discussion on this wonderful question. Here goes.
Is the Enchantment arrow green, yellow, or a combination of the two?
yeah that's it...dumb i know but i really don't care...what do you think?
Enchantment question
Gianakas
Arya Nibelrund
Me thinks the enchantment little arrow is only yellow 
zelira
It's yellow, pointed up.
Zui
Yellow.
Hengis
Anything that has a positive effect (not only enchantments) has an upward pointing yellow arrow and anything that has a negative effect has a downward pointing arrow that may be purple, brown or green depending on whether it is a hex, a condition, or poison.
Zakarr
Poison is condition.
RotteN
poison turns your HP bar green, but the downwards arrow is still brown :P
Liu
They dumb it down for the retards you see in Guild Wars. Durr hurr arrows pointing up = good. Everything else = bad. ZOMG PURPLE AND YELLOW ZOMG!!!!!oneone
Caelus The Fallen
The arrow is yellow, but if your monitor colour settings are a little off it can look a kind of green-yellow. I would also say the border around an enchantment on your status monitor is green; or at least a greenier yellow than the arrow.
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Greenier is a word, honest....
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Greenier is a word, honest....
TheMosesPHD
For my settings the enchant arrow is right on the border of both colors, I think of it as yellow but sometimes I might percieve it as green. (mayhaps it depends on my mood ) Like the above poster, my border is sort of a green-yellow/lime green. My NPCs on the minimap are definitely a yellowish green, and I'd definitely never call it yellow, though the ol' game manual calls them yellow, and I've heard a few ppl call them yellow.
) Like the above poster, my border is sort of a green-yellow/lime green. My NPCs on the minimap are definitely a yellowish green, and I'd definitely never call it yellow, though the ol' game manual calls them yellow, and I've heard a few ppl call them yellow.