As dunster says, it is up to you - whether you want the quilting to stand out or blend in more. There are no hard and fast rules, but if you have some scrap fabric in the colour you want to quilt, I would definitely do a few test stitches to see how it looks before going on to the piece you want to quilt (I learned this the hard way.....). Sometimes the way you think it will look is completely different to how it actually turns out.