Hi tasview.
I'm new at this too - I am certainly NOT an expert in this field. However, I was reading a book just this morning which addressed your very question, and so, I thought I would share with you what I've only just learnt myself.
The book is
"Star Ware: the amateur astronomer's ultimate guide to choosing, buying, and using telescopes and accessories (third edition)", by Philip S. Harrington, published in 2002 by John Wiley & Sons (USA). I borrowed it from my local library.
About lens coatings generally, Harrington writes:
"By applying a thin layer of magnesium fluoride onto both surfaces of the lens, reflection is reduced to 1.5%. A lens that has been coated with magnesium fluoride will exhibit a purplish tint when held at a narrow angle toward the light. If the coating is too thin, it will look pinkish; if it is too thick, then a greenish tint will be cast. Uncoated lenses have a whitish glint. ... multi-coated lenses reduce reflection to less than 0.5%. These show a greenish reflection when turned toward the light."
About ruby-coated lenses specifically:
"What about ruby-coated lenses? Ruby, or red, coatings are quite the rage in certain circles, although documented evidence of their real benefits remains rather dubious. Manufacturers tell us that they are best at reducing glare in very bright light, such as sunlit snow or sand. Whether this is true, I will leave for others to debate, but ruby-coated binoculars offer no benefit to astronomical viewing and, indeed, may actually work against stargazers."
I don't know if he's right or not, (perhaps someone else can confirm/deny this), but I hope it was what you were after. Although actually, when I think about it, it probably wasn't what you wanted to hear!
Cheers ...
