Paint a piece of paper with water and then use a dropper to drop coloured water onto the paper.
Pour milk onto a plate, add drops of food colouring and then add drops of dish soap to watch the colours mix. (Note: it said any kind of dish soap would work but I tried 2 different kinds and didn’t really get the results I had seen on Facebook. It might be trial and error with which kind works the best)
Spray bottles filled with coloured water. Kids seem to love spraying things!!