Please don't paint the house gray. It will look out of date in a couple of years. While gray has been a huge trend in interiors for the past few years, fashions will soon shift to using much less of it. You already have a gray roof so it would be too much gray anyway. Since you like yellow, what about making the house that colour? Benjamin Moore HC-29 DUNMORE CREAM is beautiful. Shutters could be BM 2135-30 NOCTURNAL GRAY and the front door could be BM 2135-10 BLACKTOP. I've actually taken the colours you mentioned but put them on different parts of the house :) See the photo below that will give you an idea of what it might look like.

The other thing you should consider is the look of your neighbourhood. You will want to fit in with what the other homeowners have done. That may mean just freshening up the white and changing the shutter and door colours. I hope I haven't confused the matter! Just trying to help :)