If I want to frame something which is white, what colour what look good for the backing paper?

A nice grey.

 

I was thinking dark green myself......why grey?

Black.

Neutral, and black would be too stark against the white.

Depends how colourful the main picture is. If it's full of greens then probably green would [censored] well, although I'd say a nice kind of faded green (not pale, but with a grey-ish tinge).

 

Plus you know it is winter. Winter colours and all that ... !

 

I'll for a green then.

just a thought if you had a scanner could u not scan image in and try various colour backgrounds