I paid 2.00 was that to much?ORIGINAL: BillinMo
I agree with Sparrow75 (Chris) - it's a Hemingray blue. The color's essentially identical to what jar collectors call "Ball Blue" but the thickness of insulator glass tends to show off the color better than thin jar walls. Both the Ball and Hemingray factories operated in Muncie, Indiana and both used sand from the same source that had enough trace minerals to produce the blue color. It could include very small amounts of cobalt... I'm not certain.
This is a telephone style, Hemingray 16, CD 122, made in the 1920s. By that time Hemingray would have only deliberately added cobalt to color the glass mixture if a customer specifically ordered cobalt blue products, and to my knowledge telephone companies weren't very interested in special colors.
Hemingray blues make a nice change from the typical aqua from around the same time period and look really pretty in a window, but it's not a rare or valuable color. An insulator like this might be worth a few dollars.