I had the same problem. Im a bit new to Zmud, so i spent a couple of hours trying to fix whatever i had messed up (grin).
Im told that the colour change is caused by the update the gods are doing at the moment. It seems like many of us experience different, and sometimes quite creative, colours on our text. Whenever i type gmw, and sometimes qw, it goes dark green.
I don't tink there is anything to do about it, we just have to be patient. I'm so used to the dark green text now that I might even keep it *giggle*
However, you might want to ask a god about it. Rumors often turn out to be untrue in here.
Written by my hand on the 15th of Midwinter, in the year 1093.