When I replaced mine, the stock black ones had become very hard and were not sealing well. I have used the grey ones and even reused them after a valve adjustment...no leaks after 1 years use, then reused after valve adjustment....5000 more miles and no leaks. I didn't torque the bolts...just tightened down good after the shoulder bolts seated.

 

I bought 6 from Cummins and got gray. I bought a head gasket set from Cummins, and got 6 gray with it also. I would think gray is about all they have. but I will tell you this, if you ever take the cover off and it's still hot, you will say prayers 7 times a daytrying to get it back on. Every black one I've seen that came on the engine, was so brittle they would break when you removed um from the covers.

..Preston..