[header] How to decorate a fondant cake [title] Tint the fondant before using it. [step] Put on a pair of food service gloves and about 6 ounces (170 g) of fondant on your work surface. Ensure that the surface is stain-resistant since the food color can also tint it. 
Squeeze 1/4 teaspoon (1.25 g) of gel food color onto the fondant and use your hands to knead in the color until it's evenly distributed. If you want a brighter color, add more tint until it's as vibrant as you want.