I did very well.
Discoloration will occur if the session is too long and/or the clamp is applied too tight.
Start with minimal tightening and shorter sessions. You can gradually increase session time, and then intensity.
I had discoloration in the beginning, but once conditioned, it didn't happen again, unless I went with a very intense session.
After a couple months, I incorporated bending into the sessions. This got me great gains. ** NOT FOR BEGINNERS OR INTERMEDIATE CLAMPERS **