Colourset rows:
8 - Shorts
13 - Pattern Colour 01
14 - Pattern Colour 02

To swap between Black & White easily, turn off the diffuse/spec/gloss check marks on 13 or 14 and turn them on in the opposite row 
(Can be down in Penumbra under Advanced Editing -> Materials -> Choose from dropdown)

Turn off the shorts dye by turning off the checks on row 8 - Shorts will be black by default 

psd included to allow for pattern customization. Edit the pattern by editing the mask layer on the group and saving as a png