Here's a list of color codes for a Riso RP inks. These have been tested on a Riso RP3100UI model, I'm uncertain about compatibility with other RP or similar models. I don't think it's necessary to change the color code on the drum after swapping ink colors but if you want the printer to show the proper drum color on the display you can use this codes to update the drum settings after swapping inks. To change the drum code: 1 - Start up in Test Mode (Hold Left & Right keys while turning on the printer). 2 - Type: 587, press Start. 3 - Select the new color code, press Start.