To differentiate similar products and to identify certain connections, for example polarity identification for customer processing, various colored glasses can be sealed into the glass-to-metal seal. The coloring does not alter the properties of the glass, except for filter glasses sealed into caps. In this case, the coloring determines the optical characteristics of the glass. Another exceptions is glass seals for applications in opto-electronics. In this case, the light transmission of the glass can be considerably reduced by coloring.
Available colors for glass-to-metal seals include: green, blue, brown and black, as well as neutral glasses.