In addition to Optiboard I'm also a member of a vintage clothing forum, and, of course, have particular interest in the vintage frames that users buy/display. Something I've noticed is the prevalence of emerald/bottle green lenses in frames dating from the first half of the 20th century. Some users who actually use the plano lenses even voice a preference for them over gray or brown. So my question is, why/when did the color fall out of popularity? Was it simply a factor of G-15 cornering the market on "green" lenses?