Image structure

[aka]

Hi,

I am begining with gimp and please need an advice ; take a look to the jointed picture.

My question is : which is the best way to have :

1. the green only in the red shap (NO green out the red shape).
2. the blue only out of the red shape (NO blue in the red shape).

I tried several things, but I think that people with experience can help me a lot !

Thanks,

aka