They filled the paper cups about half-full each with water, then added about 20 drops of food dye to each, making a cup of blue dye, a cup of yellow dye and a cup of red dye. They could also make other colours like green (using yellow and blue together) or orange (using red and yellow) or purple (using red and blue).
When the eggs were completely cool, the bears very gently added them one at a time into whichever cup contained the colour that they wanted their eggs to be.