I agree with Karl. If you go to Lowe's or Home Depot or even any lumber yard and look through the stack of poplar you can find a lot of different colors in the boards. There is varying amounts of color and some of them can have tan, brown, green, yellow and purple all in the same board!
Short of using some lime Kool Aid (without sugar) to dye the wood I can't think of any other readily available wood that remains green or any other dye to use. Of course that all depends on how dark of green that you need also.
Rog