Customise the Visual Studio colour scheme per solution
There is an extension called SolutionColor which is available from Tools -> Extension and Updates -> Online and search.
In later VS it is located under Externsions => Manage extensions
When installed, right click the Toolbar and add Solution Color.
I don't think you can get different color schemes configured automatically and have it switch by what solution you load.
But you could try the VSCommands extension, they add something called Solution Badges that might make your life a bit easier.
Get the extension from the gallery at http://visualstudiogallery.msdn.microsoft.com/c6d1c265-7007-405c-a68b-5606af238ece