First up is a technique for all fused appliqué fans. I have run into this problem myself....you want to use a light coloured fabric for your appliqué and you want to put it on a dark background. The dark background can 'shadow through' and change the colour of your appliqué . Or if the background is a print, you can see the print through your shape.
I ran into this issue when making the igloos and polar bears for my Our Home and Native Land quilt in my first book, Quilted Havens. The background behind both these shapes included Northern Lights fabric so my white fabric no longer looked white.
I used batting behind my shapes (trimmed slightly smaller than the igloos or polar bears). It added a bit of padding to these shapes as a bonus. However, I had to be very careful to position the batting correctly so it didn't extend beyond my applique shapes. I remember it being a bit difficult with the polar bear legs. I think I had to trim some wisps of batting after I stitched around the shapes.
I found this great McCall's Lesson about using an additional layer of fabric instead of batting. Here is the link:
When fusing light-colored appliqué shapes to darker shapes below, sometimes the darker fabric will show through, detracting from the appearance of the appliqué.Have you had this problem with fused appliqué? How did you solve it?