This would've been a good and competitive fight around 2017 when Strickland lost to Usman at WW. Sean is better suited to MW (probably drained himself cutting to 170) and Colby was in his prime then--while Sean was still fine-tuning his style. At his best. Colby was the true cardio machine, with both wrestling and very high striking output, though his striking wasn't powerful or very technical. Still, it was hard for other fighters (besides Usman) to match his pace, and Colby has always been very durable with a great chin.
Colby has slowed down a lot and would be a sparring dummy for Sean at this point. Best case he gets 1 or 2 TDs but can't hold Sean down for any length of time. Even DDP couldn't keep Sean on the ground for long, and he's much stronger and bigger than Colby.