Dirty oil

Did you also change the oil filter?
Some engines hold a bit of oil even with an oil filter change and that could be your issue and if you did not change the filter it will ad discolored oil back into the system.

Paw Paw

Pretty standard. Next time you change the oil cut the filter open and make sure there are no metal flakes inside

You don't get every drop of old oil out each time your drain it.

My Yamaha is the same way.

I also have a separate strainer filter I clean after each oil change and if that and the regular oil filter look good, I'm ok with the oil "looking" dark.

Sorry for the dumb question but... are you getting the old oil up to full operating temperature before draining it?

Did you change the brand/type of oil you were using or just add a fresh change of the same kind of oil?

It could be some sludge/deposits getting cleaned out if you went to a better oil with better detergent performance.

Seems pretty quick to go totally dark from just a ride up and down the street but not unreasonable. Also, what the others said about residuals being left could easily be the cause too.