L to R: California CD 161 green/purple two tone, CD 161 aqua/purple two tone, CD 162 sage green/purple two tone (there is some sage green in the skirt) and CD 161 grey/purple two tone.
Question: How many colors in a Cal two tone? Answer: 2 plus.
It is actually not difficult to find a California insulator with two different glass colors (especially in California state!). However, the high values referenced in the Briel Price Guide are reserved for the best two tones that have great visual separation of the different colors and great balance in the amounts of each color. A large amount of dome glass increases the visual appeal of the two-tone coloration. Note that foreign contaminants in the glass often add additional color streaks to the glass and traditionally the contaminant color does not count toward the two tone determination. For example a sage green signal with amber swirls would not be categorized as a two tone.
Good two tones are most commonly found in the CD 161's and with much difficulty in all other California CD's. The smaller CD's (102, 112, 133,160 and 187) have the added disadvantage of a small surface area to present the two tone coloration so a generous amount of dome glass, if at all possible, is a more significant consideration.
Many California colors tend to be light and pale (i.e. pastel) and the insulators really need to be displayed in a backlit display box or cabinet in order to fully appreciate the diverse range of California glass colors. I prefer the 5,000K daylight fluorescent tubes to display my glass. If you cannot display at least some of your insulators this way, I would advise you not to collect the California two tones. Given what you have to pay for one, you will never be able to fully appreciate your purchase if you cannot display it properly.
If you already have some California two tones, you should practice viewing them under all types of suboptimal lighting conditions, so you know what one looks like on a dealer's table, antique store shelf, outside garage sale, and eBay auction photo. The light Cal two tones and even some of the better ones are easily missed or dismissed by sellers because of the lack of perception of the multitude of colors. Railroad soot, dirt, environmental haziness can easily mask a great Cal two tone!
Looking for good two tones in all California CD's except CD 161.