The biggest difference between the three types of food colouring is the level of dilution. The less liquid the product is, the more the color is concentrated. Gel or paste food coloring can generally be used together with liquid coloring. This might be a good cost effective solution. Gel food colouring is more concentrated, so you will need less of it. Powdered food coloring doesn't need more liquid, so great for painting meringues, macarons and chocolate.