Place the marshmallows, butter and vanilla extract in a large, microwave-safe mixing bowl. Microwave on high for 1 minute. Stir the bowl. If the marshmallows have not fully melted, continue to melt in 15 second increments until fully melted. Stir the bowl between each increment. Add vanilla and stir until blended.
Arrange your medium mixing bowls. If you are making 3 different colours, you’ll need 3 bowls… if making 4 colours, you’ll need 4 bowls, etc.
Divide your marshmallow mixture, evenly, amongst the bowls. I am making 4 colours so I am dividing it 4 ways.
You’ll need to work quickly because the marshmallows begin to set almost immediately. Add a few drops of food colouring to one of your bowls and stir to get the colour you would like to see in your Easter egg. Add the other colours to the remaining bowls and stir.
Divide the Rice Krispie cereal evenly amongst the 4 bowls. Stir to fully coat the cereal.
Now we are going to get our hands a little dirty. Spray your hands with cooking spray. Spoon approximately ¼ cup of the coloured rice krispie treats into your hands and press it into an egg shape. Lay the egg on a sheet of parchment or sprayed rack. Continue doing this for each colour until all the treats have been formed into Easter eggs. Let the eggs stand to set for at least 20 minutes before enjoying.