(L to R): CD 161 in a yellow citrine, CD 161 in a green citrine, the next three CD 161's are in different yellow shades, and a CD 152 in a light yellow. The citrines are easily misidentified as yellows because of their scarcity and thus inexperience of collectors in discerning the differences in color. Many California insulators were made in yellow color glass that naturally changed color to various shades of purple when the insulator was exposed to sunlight. Some collectors have experimented with California glass by heating the insulators to high temperatures, which in certain instances reversed the color from sun-induced purple back to yellow. Signs of this post-manufacture heating can sometimes be discerned after a careful examination of the yellow California. In other instances, visual evidence of post-manufacture heating is absent. Some collectors have refrained from acquiring yellow California insulators because of this problem of artificially-induced glass color change. Email me privately for information on how to detect such heating.
Theoretically, there should be a yellow color for every California CD that has purple examples. In practice, yellow insulators are scarce in all (purple) California CD's except CD 161 and CD 162.
I am seeking yellow examples in the following California CD's: 133, 145, 178, 187, 200, 208, 1131