This is a NEW option in the color settings menu of FLexi. It allows you to "tweak" colors like gray, red, gree, yellow etc etc,. so say the yellow you are printing has 80%Y 8%M and 2%C. Turning on PURE HUE for YELLOW and CLEAN COLOR might remove the 2%C giving you a better yellow. The tolorence is set as a way to tell Flexi how much "color smoothing" it should do. You'll have to experiment a bit. Ill be doing a video on this soon.