If you look at the On Ringo Lake quilt pattern (and my hats off to you for tackling that pattern!), it depends on a lot of value contrast to make the design pop. The purple and yellow are the colours you want to pop? Have a look at one of the quilt blocks, attached. You need to add in a very low value background, like a very pale grey, white or cream, and a luminous colour...maybe a coral to pop the purple and mustard. One way to choose colours that pop each other is to choose a balance across the colour wheel with your main colours. So the colours that are equidistant from yellow and purple on the colour wheel are red-orange and turquoise.