To reproduce stable colors with the machine, use pre-output image quality adjustment.
Understand the image adjustment flow (which timing, which image quality adjustment, in what order), and then make adjustment as needed.
Image Quality Adjustment Flow of Image Controller IC-602
Image Quality Adjustment Flow of Image Controller IC-308/Image Controller IC-310
Screen Selection (Adjustment Flow When Changing the Screen)
Density Balance Adjustment (Adjustment Flow When Changing the Screen)
Maximum Density Adjustment (Regular Adjustment Flow (High Accuracy))