For this I placed cups of different color water in a bin, I used food coloring to color the water (and placed everything in a bin to make clean up easier)
Then I gave my kids spoons, and droppers to add the water to bowls and a paint tray.
Very nice colors!!
My 4 year old really got this activity and loved trying to make new colors while my almost 3 year old just wanted to pour everything out. They both had lots of fun learning and at the end when all the water turned a deep blue we did a race to fill the cups just to add to the fun.