As long as you make sure the grey SC has some texture, an interesting pattern or is made of a fabric not typically used for suits you'll be fine. Brown jackets certainly look great, but it can be harder to pull off for younger guys like myself, as it's not a typical color for people my age.
It's easier than you think, I think. Try dark brown cotton, for instance. All your light blue shirts will work beautifully with it.
This is coming from an old guy, though.