Americolor has peach.
http://www.sweetbakingsupply.com/peach-americolor-food-color-p-247.html
And so does Wilton.
http://www.google.com/products/catalog?q=peach+wilton&hl=en&client=safari&rls=en&prmd=ivnse&biw=1256&bih=1084&um=1&ie=UTF-8&cid=10243665013542146800&sa=X&ei=pTa4TajgIILg0QHq4-jfDw&ved=0CGAQ8gIwAA#
And just a touch as a little goes along way...If you add too much it's hard to bring it back..
If not, what colors should I mix to try & get peach?
There are many variations of peach; flesh-, orange-, rose-ish. If you have a swatch you're trying to match, it's easier to get the correct shade desired. When I mix peach, it's mostly yellow with a tiny amount of pink. If you add orange or use too much pink, it becomes more of a salmon color. If you want more of the fleshtone color, it's probably easier to buy the flesh color paste or liquid.
You may need to use a powder color depending on how you're using the royal icing; both Wilton and Americolor have glycerin in them.
I've used both Wilton and Americolor colors with royal icing with out any problems.
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