Fondant is a versatile medium for making decorations to go on cakes, cupcakes and cookies. It resembles modeling clay and can be colored and painted as desired. When coloring fondant, make sure you have enough for your entire project because if you come up short it can be difficult to get the correct shade to match the previous batch. It is best to smear drops of color and knead the fondant thoroughly before adding more color.
Knead white fondant until it is smooth and pliable. Work on a clean and grease-free surface so that the fondant does not break down.
Add three to four drops of black color using a toothpick or a knife. Smear the food color at random spots on the fondant.
Knead the fondant, distributing the color evenly and making sure it is not marbled. If the fondant looks more purplish than grey, add a drop of yellow and red to deepen the colors. Use the grey fondant as desired.
Tips
Do not add too much food color as it can give a bitter taste to fondant.
References