You can do this. Define your colors (White = WH, Blue = BL), then when giving your multicore wires (or standard wires) a color you can give it a stripped code e.g. "WH/BL" ("/" for the stripe). When I do this I am able to press the "..." and multi-pick which colors are needed.
Let me know if you have problems doing this,
thank you. I wasn't aware the colour pick dialog would allow me to select muiltiple colours. Depending on which value I select first, I can even choose between wh/bu and bu/wh. The error message I got was probably related to VeSys not liking "/" within a colour code, which perfectly makes sense. The error message could have been more specific, though.