DO NOT play g6 in these circumstances unless you avoid playing e6. Playing both e6 and g6 is VERY weak on the dark squares. Seeing as that you are normally a d5 player, The setup with d5, c5, e6, Nf6, and Nc6 (not necessarily in that order) is really solid for Black.
Ideas vs. Colle & Reverse Stonewall w/ or w/o f4

Nothing wrong with playing d5 in a closed game.
Why would the OP think g6 would be useful in this position? I should think c5 and Nc6 might be more effective. Maybe with a b6 & Bb7 if possible.

Hello, thank you for the responces.
The reason why I thought g6 was useful is because I saw it in an MCO without any real explanation of theory. And I thought the reason for it might be to help block the attack by Bd3 when black castles short. so the basic idea is to attack the center with c5 since white doesn't want to play c4 first & combine that with the idea of exchanging the light-squared bishops ?
As Black I'm looking for Ideas against the colle
particularly after 1.d4,d5 2.e3,Nf6 3.Bd3,e6 & an eventual g6
or are there other ideas I should look at like Bg5 or c5 or both. Any help would be appreciated.thank you