Some people have no vision! I have various pops with different glitters/foils etc next to the normal shellac colour I then have the co-ordinating glitter on top & 99% of the time they'll go "oh yeah that's lovely I'll have that!!" I charge an extra £3 on top of the regular shellac price more for the time factor. I think an extra £5 can sound a lot to some people on top of their normal service but for £3 most people don't think twice! HTH
I wear a lot of them on myself, I also have a range of colour pops and post ALL my photos on my facebook page. My clients come in and say 'I screen shotted these nails that you did I love them!' My clients are obsessed. I only charge 50p a nail for rockstar and £1 a nail for hand painted art. I also do a lot of stamping!
Maybe you should try showing them off a bit more? It took a while for me but I was persistent. Makes manicures a lot more fun and interesting!