If I have the fabrics next to each other I can tell if they will look good together. Lots of times I can match by memory as well. My main issue is getting too many that are in the medium to dark range and not enough in the lighter range.
I've been matching colors for as long as I can remember so I don't really know if it is a natural talent or if it was something learned. I do know that I've gotten better over time with the memory matching. So there is a "practice makes perfect" component.