Here is a link to the Wilton color chart. HTH!
http://www.wilton.com/cake/icing/colorchart.cfm
I've made it before and used leaf green and just added small amounts of yellow until it got to the right brightness i wanted. A little bit of yellow goes a long way.
Also, if you have access to a cake supply store near you, Americolor makes one called "Electric green" that is a very nice bright lime green color!!
Valerie
I use lemon yellow and slowly add kelly green. It's perfect lime green!
I have an actual lime green gel color. It's made by Cake Craft (http://www.cakecraft.net).
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