Above is the design. The output looks as follows:
Only respecting the disallowed combination given for 'with chemicals'. What am I doing wrong?
I think you want to replace the AND in your disallowed combinations script to use an OR instead, like this:
( X1 == "L1" & X2 == "L1" ) | ( X1 == "L3" & X2 == "L3" )
In addition to @ih's suggestion, I wonder if you are setting up an impossible design given the model you specified. It seems like Coloring Process and Color Fading are confounded.
