Glass Bead have been dated back to at least the Roman times. They are usually categorized by the method used to manipulate the glass - wound beads, drawn beads, and molded beads. There are composites, such as millefiori beads, where cross-sections of a drawn glass cane are applied to a wound glass core. A very minor industry in blown glass beads also existed in 19th-century Venice and France.
Three-Tone is when a piece of jewelry has three types/colors of plating.