This method of labeling is relative to the weaving, not to the tablet itself. The cloth/face hole is always on the top nearest the weaver, so it won't always be red.
Instead, if you turn the tablet forward repeatedly, it will be red, then green, then yellow, then blue. Those colors will appear in the weaving in the same order too, moving away from the end of the warp.
You can use this to draft your patterns, because the way the tablet is threaded can be directly related to the way the woven band appears.
You can't do that unambiguously with ABCD labeling.
Yes, I think this is very important!