Sap Green is a beautiful yellow green that you can use straight from the tube onto paper and it would not look out of place. Add Ultramarine to it and you can have variation easily, add Burnt Sienna to that and you have have a much darker shade that looks like shadow green.
Daniel Smith has recently changed the formula of Sap Green from the original combination of Quinacridone Gold PO 49 and Phthalo Green PG7 to Quinacridone Burnt Orange PO48, Nickel Azo Yellow PY150 and Phthalo Green PG7.
These are some colour swatches and mixes I've created to compare the two. The new formula looks very similar to the original so I don't think I'll be missing anything.
Here's a quick sketch coloured with Sap Green, French Ultramarine, Burnt Sienna and Pyrrole Scarlet. This new Sap Green performs the same when it comes to the typical mixes that I use.
It's a shame that Quinacridone Gold has ran out but at least the alternative is good enough.