If you take a detailed look at the labels of rollers (cobs), you may be quite surprised at the variety of styles! The following chart shows major changes. In general, the red labels are oldest, and then the white and yellow. But there appears to be no discernable pattern to truly “order” labels according to manufacturing date. Due to reissuing of older rollers, and evidently the mixing of current labels, anything is possible.
In addition, there are no certain pairings of labels. Although the matching circles are often found together, some are not. Several rollers even mix red and white labels.