You also might be able to get the color you want with the spray by getting a can of green and a can of brown and playing around with both of them to get the color your friend wants. Both of those colors should be easy to find.
I don't think this will help you, but I've used liquid shoe polish on my hair before, with no ill effects (that I know of)! I remember using it as a kid for various costumes. As an adult, I did a Wolverine costume on short notice, but I couldn't find any of the temporary black hair color spray (I have light blond hair). So I used Kiwi brand liquid shoe wax in black. It stays in well, didn't run or get on anything, and I think it washes out as easily as the spray can stuff does. I don't think they make any in green though, just the more common shoe colors.