Seat belts: Black. If the car was optioned with C15 (Deluxe Seat Belts) it would have Red belts. Otherwise Black. There are exceptions though. Some Challengers came with what appears to be a standard buckle with Red webbing. (Perhaps Barry will explain in more detail?)
I know of some early built Barracudas with Red interior and Black belts.
Steering column: Standard dash cluster came with a black steering column. Rallye Instrument Cluster came with a Red column. Both came with the Red 3 spoke horn pad. Again, there are some exceptions. Early built Red interior Challengers with the Rallye Instrument Clusters came with the Black column. Such as the Promo cars.
My Red interior `cudas (203 & 421) both have Black seat belts and Red steering columns (A62). Both original cars when I purchased them.
Ola