Dave,
The 1946 ~ 221's were painted Grey, the 1947 ~ 221's were painted Black.
As to repainting your locomotive and tender I'm sure that the paint can be matched if it is not available commercially.
Personally, I don't believe in repainting unless the original paint is totally wasted. When you repaint, you destroy the history, love & play the train has received over the years, taking away the originality & individual personality the locomotive has developed over its lifetime.
So, unless it's a total piece of junk paintwise, I'd just clean it up really well and apply a coat of wax to it.
Dave