ProGel Professional Grade Food Colouring UK. ProGel® concentrated colours by Rainbow Dust Colours are the new standard for food colouration. Highly concentrated, only the smallest amount of ProGel® is required to give a deep rich colour to your creations, meaning that our tubes last a long, long time! Simply add a small amount to your sugarpaste, marzipan, buttercream etc and watch it transform into your desired colour as it is mixed in.