Impress your friends with Colourfuel and its amazing colour change effect, just add cold water and watch the white bottle magically turn blue! This ultra-lightweight, durable flask, packs 600ml of liquid into its small size. Perfect for adults and kids on the go. Watch as the water splashes around the bottle, with mesmerising effects on the outside, or fill slowly and watch as the blue line rises from the bottom as you fill. Once blue, apply the heat of a hand print to create fantastic effects.