If the fluid is discolored, it usually smells bad too.
I change trans fluid about twice as often as recommended. Cheap insurance.
I usually drop the drain pan , clean out the "muck" sitting on the bottom of the pan (As stated before , clutch material , completely normal). New gasket and refill. I don't change the filter , as stated before, it does not filter much , it's more like a strainer to prevent large debris. Then refill.
This will change only about 70% of the fluid. I steer clear of the oil change places offering overpriced "Trans Fluid Exchange" or "Flush" services.
P.S. in order of preference : A trusted independent repair shop , a true "transmission" repair shop, or the Dealership $$. The oil change places can barely change oil without screwing something up , or just $crewing the customer.
Make sure the correct fluid is used. many late model cars require a specific fluid.
“The finance industry is 5% rational people and 95% shamans and faith healers.” - Charlie Munger