Yes, that is usual Convict breeding behaviour. They will make a "nest" by removing gravel (usually right down till they reach the tank floor). They may also move plants around and build a little shelter around the nest. If you have caves, they are probably chucking out the gravel from inside the cave as they like to lay their eggs on a flat surface.
Hmmm, I'm not sure about the male changing colour though. I don't have standard convicts with stripes - mine are short bodied pink convicts and the only colour change I notice is that the female's body goes very orangey at the top and underneath/around her belly.
They dart at each other back and forth and the male swims around the female in circles, brushing against her. Then the female will lay her eggs in the nest and the male should fertilize them. The female then stays guarding the eggs the whole time, barely venturing away for food even. You have to make sure she does eat something otherwise they can get run down very quickly and become ill due to the stress of the whole process.
If you have other fish in the tank with them you'll see the male convict chasing them away constantly - they become extremely territorial and aggressive at this point.
Hope that's helped a bit - Athena
