Measure your light switch and add a border.
Cut out the square/rectangle. Snip from the corner of the border to the corner of the middle so that you can fold.
If the corners overlap cut a half moon shape.
Put something down to protect the surface and choose your colours ( i used red, yellow, green and blue ) And mix them with water. This will make it easier to spalt.
Now....SPLAT. You can do this as much as you want.
Wait to dry.
You can use a hair dryer to speed up the progress ( i let it dry naturally ) But make sure you stick it down with blue tac so it dosent blow away!
To make it last longer use some sticky back plastic. Refold and cut the corners.
Measure where the switch is and cut it out.
Stick onto the light switch with blue tac, sellotape or double sided tape.