I'm guessing the black is for applications where the user might not want an orange color showing. Ie Motorcycles, boats, atvs, machinery, etc
The 7317 fits Mercury applications for watercraft, trailwagon atvs, Caterpillar engines, and quite a bit of others. My guess is the black version is for these applications. Why? I dont know, user preference?
Plenty of brands out there have two or more of the same filter just painted differently. Orange would kinda stick out like a sore thumb on a motorcycle, although I dont think this filter has a motorcycle application, I'm sure theres a boat nut out there who doesn't want a bright orange can on his red and black mercury engine.
IIRC K&N has black as well as chrome HP filters (the ones with the rust nut) with the same application number as the white cans for motorcycle and watercraft engines.