What to use to touch up undercoating?
 

I have some areas under the car that could use some touch up of the factory undercoating. It looks like it's grey.

I picked up some 3M rubberized undercoating at my FLAPS, but it's black. It will work to protect the car but I'd prefer not to have the black patches on the gray undercoating.

Is there anything I can get in a spray can that's easily applied which will closely match the factory undercoating?

The original color is not available from Wurth anymore, but I believe the current ones are paintable.