Originally Posted by wevans
I have a question about oncidiums too. My oncidium leaves have purple spots on them. What does this mean, the roots are healthy as they all have new tips on them.
A pic of your plant would be nice in order to be certain of what the spots really are.
If you want my best guess at what's going on with your Onc - based on your description, I think your Onc has produced a pigment called anthocyanin in order to shield itself from excessive amounts of UV light.
Should your plant really have produced anthocyanin pigments, it is not of major concern.
If by any chance you have a suspicion that it is not anthocyanin pigmentation, I highly recommend posting a pic asap.