First, open your latest version of CatalystEX by clicking on the File tab located at the top left hand side of the screen, and then clicking Open STL.
Select the desired property settings.
Click on the Orientation tab and press Process STL.
Press Step Up and/or Step Down until you get to the layer that you wish to switch the color.
Press Insert Pause and the border of the design will become highlighted in white.
Next, hit Add to Pack and click on the Pack tab.
Lastly, click Print and your file will be sent to your 3D printer.
Now you need to switch the material cartridge to the desired color. It is always best to purge multiple times to assure that the old color bleeds out, especially when switching from a dark to light color.
Next, hit Resume on the printer and your job will finish with the second color.
Below is an example of a file printed with the colors white and black. The printed version is on the bottom and the original is on top.