if it's just on the sight glass and inside the filler cap, it's quite normal, I do a 5 ile ride to work and it's exactly the same as yours atm, It will be sorted for a while tomorrow as I'm heading out to West Wales for a day in the lanes.
It'll be back by the end of the week... the mrs 125 doesn't have this 'problem'.
Jen laughed when I said you had 'milky spy hole'
Some have attributed it to pumping action of the twin engine on a bike that gets used through winter for short commutes, sucking in moisture through the air box breathers and the engine/oil not getting hot enough to vaporise the moisture and expel it from the engine casing.
You won't likely get any sense from Dragon Bikers- just scare tactics telling you to get it sorted ASAP.