I really love this stamp. It's one of the Papermania ones for this year (it's PMA 906900 filigree Christmas tree) if any of you are looking for the code for it.
To get the mixed colours on the tree, I just used 4 different shades of green.
Start with the lightest of your colour first, this way you can always add more ink!!!
If you start with the darkest colour that will be all that you see.
I used one of the darker shades to ink around the edges and then a velvet ribbon to match.
My decorations for the tree are little buttons.