California 2-tones with purple as one color indicate that at one time the original 2-tone was yellow and another color before the yellow portion was purpled by sunlight. Nothing rare about the yellow or blue glass colors, but the combination in one insulator is unheard of. This 2-tone CD 161 has a nice balance of both the yellow and blue and was purchased through a friend at the Muncie National, coming out of a collection in Iowa. There are other less colorful examples of this 2-tone combination. I own a citrine CGI pony with some blue dome swirls. There is a yellow baby signal with one blue swirl and a couple of yellow helmets with a single blue swirl too.