I tried this evening with just the light from the machine, it was better, but still couldn't see well. The quilt is throw size, so there was room on the frame for a lamp. I have one with a positionable arm and I directed the beam across the quilt. That seemed to work the best. I went slowly and finished it. I checked the back of the quilt for places I missed before I removed it from the frame, and found & fixed a few spots. I think I'll stick with contrasting thread.
I now have vast respect for folks who use blending thread or (horrors) monofilament!!!!!!