Color charts for machine embroidery threads can be found at Sulky.com, Brother-usa.com and WindstarEmbroidery.com. Some of these charts include conversions for different brands of embroidery threads. Sulky.com offers thread charts that have actual swatches of thread attached, as well as printed thread charts.
ThreadExchange.com gives the option to convert Pantone, Coats, Floriani, Gunold, Isacord, Madeira and Sulky threads to Robinson-Anton Colors. Select the brands to be converted, and the list of colors is displayed. It is suggested that the online color charts be used as a guide, as variations in computer screens and printers can cause color shadings to differ.