Fondant is one of the most commonly used cake decorating icings. Fondant resembles modelling clay in texture, and can also be rolled and sculpted like modelling clay. If you're planning on decorating a cake as a castle or maybe a grey-bearded wizard, or even a cute grey pussy cat, you're going to need grey fondant. Making grey fondant is pretty easy, and you can achieve a variety of grey shades using the same method.
Knead white fondant on the counter top until soft and pliable. Use as much fondant as you will need for all the grey you require; matching the colour later with a new batch will be difficult.
Put on latex gloves to protect your hands from stain. Dip a toothpick in black food colouring and dab a few dots onto the ball of kneaded fondant. Use less at first, around four to five dots, which will make a light grey - more can be added later if you need to adjust the colour.
Knead the fondant until all the colour is distributed into it. Check the colour achieved, and add more black food colouring if you need to darken it. If you need to lighten it, knead some more white fondant and add it to the original batch.
Place any leftover fondant in an airtight container to store it. Use household bleach and a sponge to clean the counter top if any black or greyish stains are there.