We used shaving cream and paint to make these hearts, it's easy marbling for kids. The children were very impressed to see the marble pattern and it is always a nice surprise for them to see what they have created.
Squirt shaving cream into a shallow tray, drop on a few blobs of paint (we used red and a little blue), swirl it around, gently push the paper on top then peel it off carefully, use an ice-cream container lid to scrape of the paint and shaving cream and reveal the marble pattern.
We did both sides of the paper which was little messy and I made sure to use extra thick cartridge paper.
I've done this paint activity before, you can check it out here if you want instructions with pictures.