colour one door on a Blender house model

I am looking for somebody who can colour one door on my house model. The door is currently grey (no colour) and hence not visible well on the model (see attachment), and I would like it to have distinguishable colour (e.g. brown).

Note that I don't want the view (static picture). I want to have colour in the 3D model itself in Blender, so that I can look at it from angles as I want.