First of all melt the marshmallows in the microwave, using a suitable microwave bowl. You can also do this over a saucepan of simmering water. Make sure you don't burn the marshmallows by taking it out of the microwave in 30 seconds intervals.
Keep steering until it's melted. Split the marshmallow mix between two bowls and add red food colouring to one. To get all the colours, you'll need to divide the marshmallow mix and the rice krispies to about 40% for the white mixture, 40% for the red mixture and about 20% for the black mixture.
Once you have the marshmallow mixture divided, mix in the colours and then add the rice krispies and a little bit of butter to loosen up the mixture.
Next, lightly oil your round baking tin and fill one half with red rice mixture and the other half with white (original) mixture.
To finish, line the middle with the black mixture, create flat round 'ball' and place it in the middle. Pinch a little bit of white mixture and make the last detail the centre of the black ball with the white rice.
Leave to set for a while and carefully take out and serve!
If at any point the mixture sets too quickly before you get the chance to finish your shape, just pop it into a microwave for a few seconds at a time. This will loosen up the marshmallows, making the whole mixture usable again.