For retro nails I did some neon block, bright, colorful and a lot of contrast! They certainly brightened up my day, I hope they will brighten up yours too.
All the shades I used were from Orly, Skinny Dip, Beach Cruiser, Melt Your Popsicle and Glowstick. They were quite opaque, so I didn't use a white base here, the yellow needed one more extra coat than the others though. The blocks were done free-handed, so I'm quite happy with how they came out.