The purpose of this presentation is to discuss changes in color when printing with UV inkjet and screen inks. UV inks use photo initiators that cause the inks to polymerize. This reaction and the grade of photo initiator can cause a noticeable change in the ink's color after curing. This color change can revert back after curing with the presence of additional light (photobleaching) or, in some cases, without the presence of additional light. The presentation outlines the phenomenon and provides theories and ways to reduce color shifts.