A root appearing with variant form √RIT (marked with a “?”) in Quenya Notes (QN) from 1957 where it was contrasted with √DEL “fair” (PE17/151). Tolkien said it was a stem of varied significance and described its meaning as follows:

The basic sense being probably one of craft: “to complete a work or design, to add the final details and finishing touches”, hence to decorate, qualify, modify, variegate etc. Hence *raitē was used of all those details and special characteristics belonging to an individual of a sort; or to a subdivision of a kind. It could thus be translated often “peculiar hue”, (special) fashion - but it was only applied to details and characteristics that were fair (PE17/185).

The only derivatives of this root Tolkien gave were S. {raed >>} rhaed apparently also meaning “peculiar hue, (special) fashion” which in suffixal form -r(h)ed applied to colours and shapes, as well as the word rhîd of unclear meaning. Given the possible association with colours, it is conceivable this root is a later iteration of ᴹQ. laite “colour” from the early 1930s (PE21/7), but that’s a pretty big stretch.