Be very careful trying to match colors on a computer monitor. Chances are excellent that if you matched a color perfectly to something you want on your monitor, it would not match in person. Fabric color matchers are made to match other fabrics, not graphics. They go by dye content, something you cannot duplicate.
Also be aware that Moda Marbles vary greatly between dye lots and today's Christmas Red will likely be tomorrow's Almost Made It. Patrice's suggestions are excellent, as always, and I would only add that Craft Connection generally has a larger selection of in stock Moda Marbles than HoP and they do carry all the colors.