greenish tint in outside mirror

[GPSnV1]

I just returned from driving 3K during the holidays. While in TN with a temp in the 40s, I was ready to back out of my parents driveway and noticed that I could not see behind me with the left outside mirror.

There was something like a greenish tint that covered all but a small border inside the mirror. It went away with 30 seconds and everything was back to normal. No other such episode even during colder days.

I had to run to my dealer as soon as we returned home because of a warning about the oil level and I asked about this green mask. The service rep told me he had never heard of this and it didn't make sense at all.

Anyone else see this?