I have notices a few damp patches under my car after it has been standing for a while. After looking found it was a orange colour coolant. When looking under the car it seems to be dripping from the back the engine area onto two bolts from the exhaust clamp. Any ideas what could cause this. 

Thanks. 

A leak. Good that you found it before it has done any damage. The reservoir is a favourite for cracking but you will need to use your eyes and maybe a torch and mirror to find  the leak because you are closest to the problem and there are multiple potential causes. Some people warm the car up and look to see where water sprays out. Top up the coolant first before you try it.