It can be immensely frustrating as a stitcher to need to convert from one thread to another. This was brought home to me years ago when I was stitching some cross stitch pieces by Jane Greenoff. The first one I stitched was a kit my mom bought in England. It used Anchor threads. The second one, designed to go with the first, was stitched from a chart I bought here and used DMC threads.
The colors in the threads were just off enough I could never put the two pieces together.
If you’re stitching a painted canvas you have something in front of you that will lead you to the right colors — the canvas. But what if you have a stitch guide. Do you use a chart to convert? I would and then I’d check it against the canvas.
If you are working from a chart or line-drawn canvas, these conversion charts are critical for finding the right threads. About.com has collected several conversion charts in an article.
A Bit of Advice
The color palettes of the various thread manufacturers do not match. When possible stick to one manufacturer of floss or stranded silk for each project. If this is not possible, check the threads with each other to see if they coordinate.