I know what you meant
The CLS will be your L channel.
For stacking purposes the L channel can be anything, but in the program you take the pictures with, you should still call the Luminance channel the
L channel so the picture gets the information written in it correctly.
The Luminance channel could be purple but the stacking program will still see it as an L channel because of the information in the file and this way it becomes monochrome instead of purple or pink or CLS etc.