What is the colour of the number 10 on 10 downing street?

Answer 1

It's got a big black door with white numbers.

The following information is taken from Wikipedia.

Number 10's famous door is the product of the renovations Townsend ordered in 1766; it was probably not completed until 1772. Executed in the Georgian style by the architect kenton-couse, it is unassuming and narrow, consisting of a single white stone step leading to a modest brick front. The small, six-panelled door, originally made of black oak, is surrounded by cream-coloured casing and adorned with a semicircular fanlight-2window. Painted in white, between the top and middle sets of panels, is the number "10". The zero of the number "10" is set at a slight angle as a nod to the original number which had a badly fixed zero. A black iron door-knockerin the shape of a lion's head is between the two middle panels; below the knocker is a brass letter-box-1with the inscription "First Lord of the Treasury". A black ironwork fence with spiked newelposts runs along the front of the house and up each side of the step to the door. The fence rises above the step into a double-swirled archway, supporting an iron gas-lightingsurmounted by a crown.