I subscribe to the Scarlet Quince Newsletter and this was in the edition I just received. I am going to post it here mainly so I can find it again:
In 2005, DMC "merged" some of their color numbers in Europe. Changes in their dye formulas caused by evolving regulations and restrictions on chemicals used in dying meant that 7 pairs of colors had become so close together as to be indistinguishable. For each pair of colors, they discontinued one of the numbers and printed both numbers on the label of the other. Up until now, all 14 separate color numbers have been available in the US, but now the new labeling is going into effect in the US. Here are the colors in question:
You can read the full article and see an example of the new labeling in the Scarlet Quince Newsletter.