I don't think you can with DSS, but with CCDStack you can easily - just hit the create colour button and go from there, remembering to hit the apply to all button.
One tedious bit though is background neutralisation -I find even if I apply to all, it only does one, and I have to manually do the lot one by one. Thankfully, CCDStack remembers the pixel area you selected to desaturate background, and it is easy.
If you DON'T debayer OSC shots before registration, you end up with a tartan look to the stack
