Vivienne Westwood made these jelly shoes a few years back (and they are still available right now), they come in several different color combination, but my favorite one is this peachy-pink color with black hearts. I decorated a pair of similar shoes.
Cut two heart shape from a shampoo bottle, those will be the base of the heart shape. (The edge is bent, I made it flat later on)
Get a pair of (preferably white color) satin special occasion shoes. Don't buy them new, they are often more expensive than they are worth, thrift stores are often filled with them as wedding cast-offs in every color. Remove the decoration (if any).
Mix 1 cup of warm water with food coloring. I used 10 drops of red and 3 drops of yellow. The color will not be waterproof, but since it's not meant to be worn long term, it will be cheaper than fabric dye. Test color on a sheet of white paper towel first.
Use a large sponge brush and quickly cover the entire shoe in color. The color will get lighter as it dries. Let it dry for about two hours.
Finally, use a small amount of leather/patent leather/vinyl to cover the heart shape. Glue/sew it onto the vamp of the shoe.