Hi there! I'm very new to cross-stitching, and actually, don't--my sister does. But I'm an artist and my sister wanted to cross-stitch one of my paintings, so I got PCStitch 11 and gave it a whirl. Turns out that according to the DMC Color Card from this year, some of the "Available Colors" are no longer even made. Here's what I've had to find substitutes for: Any color between DMC 3867-3999 504 is now 3813 726 is now 3326 731 is now 732 781 is now 782 806 is now 3760 971 is now 740 3373 is now 407
Since those colors will be found on many older patterns, it's not likely that they will ever be removed from the list within PCStitch or any similar product. What you have to do is what you did -- find the new corresponding colors or just look and choose what you think is closest. The same issue occurs when you just don't have and can't get the colors you want/need. Some colors are only available in certain countries so that's a problem, too.
DMC happens to be the oldest, I know other companies have this same problem.