Just tried out this tip for using those big chunky chalk sticks - it works!
Put the chalk into a pot or bucket and cover with water, add a cup (5-6 tablespoons) sugar and leave overnight until the bubbles have stopped. The wet chalk has a different texture and the sugar
really boosts the colour! If you are going to be colouring the pavement, wet it first for a more intense result. Alternatively use on wet card/ wet chalk board. Try colouring other items: pinecones, rocks, polystyrene tiles, fabric and also apparently it works well as a body paint - but beware of eyes!
Try it and have fun!