your question makes perfect sense.
the one "iffy" thing about buying fabric online is that you can't put the fabrics together side by side to see for sure whether they'll coordinate or clash. the same fabric can look quite different in pics on different web sites - and different again when you see it in person. i must confess to having a lot of fabric that i discovered didn't really work once i had it in hand. that's ok for me because i'm a fabric junky and don't mind having a "new" place to start for future projects.
when i need to be very very sure fabs will work together, i try to select from within one line/collection of fabrics. i know they'll work because they were designed deliberately to work together.