The yellow or blue coatings are usually single coatings, the purple/green coatings are usually multicoatings. The coating layer(s) are clear to transmitted light, the colors appear only in reflected light due to constructive interference, the same phenomenon resposible for the raindow hues on a CD, and the colors seen when a thin film of oil floats on water. The actual color depends upon the thickness of the coating, not the material used. The substanc(es) used to coat lenses must have an appropriate refactive index for the glass being coated, as well.
Originally Posted by darinwc
Read the links. It's pretty simple on a qualitative level.
Last edited by E. von Hoegh; 04-26-2013 at 11:01 AM. Click to view previous post history.