Definately start with color. If it looks like coffee with creamer or lighter it is likely water.
Where do you live? What is the weather like lately? Stored indoors or outside? Been riding in rain? Offroad with stream crossings, even if shallow?
I am with JVB that it is likely not a serious engine problem like a cracked block or bad oil pump unless there has been some sort of trauma to the bike like a crash or some crazy over heating issue.
Condensation happen when temperatures change, think of a glass of ice water with sweat on the outside. The cold glass from the cold drink inside pulls water from the warmer air around the glass and it condenses on the glass. The crankcase in vented so there is air in the crankcase. Get the outside air cool enough and shut off a warm engine and it could pull moisture out of the air in the crankcase and condense it inside the cases. Start the bike and the running motor collects that oil and whips it into the oil, frothing it up like whipping cream.
it is easier to ask for forgiveness than permission