Hi, Bob. Color matching is certainly possible and there are a lot of tricks and tools that are not generally available. Beyond that, there is a lot more art than science involved and it is impossible to even think about telling you how to go about this from a verbal description. I suggest that you call in a pro who can see what needs to be done or at least give you some options and costs.
As far as the gaps in the T&G, are you noticing any variation between winter and summer? You should. The wood might move up to 5% or so across its width with changes in humidity. The T&G is normally nailed only at the tongue edge and it should be free to move with the changes or you could experience cracking of the boards. Can you tell us a little more about it, particularly the seasonal change?