I used 91% isopropyl alcohol from Target, no added ingredients on the label.
The stock solution was made with distilled water only, and that is still bright orange. So the alcohol must be the culprit. Or the fact that I mixed the dilute dichromates on a full moon...

I can't find it in my notes or on my books, was it potassium dichromate which can only be mixed with acetone and not alcohol, or was that ammonium dichromate?

I could mix fresh dichromates every time, but unfortunately my printing sessions are relatively short these days and dealing with powdered dichromates is nasty and requires extra care.