Can I choose the colour?

Yes. Powder coating is available in any RAL Classic colour, so you are not restricted to a short house palette. RAL 7016 anthracite grey and RAL 9005 jet black are the most common choices for outdoor steel, but a colour matched to your window frames or your interior is equally possible. Do not choose from a screen: monitors render RAL codes unreliably, so compare a physical RAL fan or sample against the surroundings in daylight before you commit.