I've got a few Aixiz 3-element lenses and they seem to be coated for different wavelengths. Are the ones that produce more bluish reflections the 650nm coated ones?
Just think about it this way: the coating is anti-reflective. So color light you see reflecting should be opposite (or different from) the color of the laser you're using it with (e.g. yellow AR coating for blue/violet, blue coating for red).
What is a red coating for? What color for 808nm? Is it possible to have someone coat lenses for you, or, do it yourself if you spend $$$? I have been googling for this answer but have not found a place to do a large 12 inch diameter lens for me yet.
A red coating is also for blue and possibly green. There are some green coated lenses for red. I own
such a lens. A coating for 808nm I think are either blue or yellow color. That would be more difficult to
figure out without knowing for sure what lens it is.
AR coatings are done in an AR coating machine. An AR coating is not a single coating, but
many layers of different coatings. There are a few places that do telescope optics that can
coat your lens.