Coolant in the oil tank?

My engine also runs on the chill side and I never see any water accumulation in the oil tank other than the aforementioned light condensation under the oil cap. Orange almost has to be coolant, IMO. Condensation from often running a too-cold engine will make the oil appear milky white. Some oil-analysis companies claim to be able to identify glycol in their testing, so that may decide the issue.

Since oil pressure is much higher than the water pressure and you don't mention seeing oil in the water, the most likely source, IMO, would be a bad seal in the water pump; the ~10 psi cooling system pressure will be higher than crankcase pressure, so a leak there will primarily be coolant to oil. Much less likely would be a crack in the top of the cylinder head into the coolant passage.

A fuel leak coming in through the fuel pump would obviously be a problem, but any dyes in the fuel wouldn't be noticeable in the oil, nor would the fuel separate from the oil - it mixes well. BUT, IMO, it should be dripping zero fuel from the pump vent hole. The latest pump version doesn't have the weep hole, it has a nipple to which a hose can be attached. In the event of catastrophic mechanical pump failure, the hose leads the fuel blowing out to a harmless location rather than spraying on the exhaust pipes. The new pump isn't that expensive ($170, which is a bargan for Rotax) and cheap insurance, especially considering the variety of ADs and SBs existing on the older ones.