If it's a painted surface, try a good polish such as Autoglym Super Resin Polish. Follow that up with a good Carnuba based wax. Don't apply in strong hot sunlight though or its an arse to get off!
Use an abrasive compound on a machine polisher for best results, that should bring the shine back up. Once polished seal it in with either a wax or sealant, I r even use both if you so wish!
Only way to get them back is a respray to match........ the GP is a red colour coat with a top coat of clear so machine polishing wont be beneficial due to it been the UV in the sunlight degrading the colour through the clear....