long explanation shortened...
Moist cold air is drawn into the crankcase thorough the breather pipes from the airbox.
This air condenses in places. Sight glass, and inside the filler cap is the usual places.
Leave the bike sit in colder weather for a few days and it'll happen without being run. But run it for a short distance and it'll appear worse. Give the bike a good long run and the sight glass will appear clear and the internal heat has vaporised the moisture. But it'll come back before too long.
it's only a concern if the oil is 'milky' in quantity.
If you hold the bike upright (centre stand) and see if the black oil will make a tide mark up the glass or not.
Every bike I've had with a sight glass has done it, and every filler cap get a coating inside.
