I've just looked at it from Google Earth and it looks pretty uniform to the three main roofs around it. So if it looks redder than the others then it has been done.
Unless they have had a recent refurb I would be surprised though because the roof cleans don't tend to come out of the store or capital budget but do tend to always be built into the refurb/extension programmes.
Also on that I wouldn't have thought it was overly moss covered because it is quite open, no trees or shaded areas.
Is it cleaner, when you next go past? and does it look any different to the other two roofs?
I like roofs
Rob