This color card from DMC, featuring real thread samples, is a handy resource for any stitcher. The guide is made with actual strands of DMC's nearly 500 colors of embroidery floss. It also has thread samples for DMC specialty lines including their metallics and variegated floss.
Real-thread color cards have traditionally been hard to come by, but DMC republished theirs to include the 35 new thread colors introduced in late 2017. Because the color card features actual thread samples, you can be assured of its accuracy.