Food colouring is a versatile culinary tool that can brighten a variety of dishes and condiments. A standard package of grocery-store food colouring contains four colours, red, yellow, blue and green. Intensity and pigment vary between food colouring manufacturers, so the same mixing ratio made with two different brands will create two different tones of turquoise. Creating a bright turquoise colour for your next beach-themed caked or cookie icing isn't difficult but does require consistent mixing with the same brand.
Start with 1/4 cup of your mixing base in a medium mixing bowl. Use this sample as your test batch to determine the shade of turquoise you want. The high concentration of pigment in food colouring means you cannot get an accurate representation of your final turquoise shade without mixing in a base food.
Squeeze four drops blue food colouring and one drop green food colouring onto the mixing base in the bowl. Write down the colour ratio so when you need to recreate the same turquoise tone in a larger quantity, you know to use three parts blue and one part green.
Stir vigorously until the colour is blended evenly throughout the base. If you are satisfied with that colour, replicate that same ratio as necessary in a larger quantity of mixing base. To adjust the tone of turquoise, add one drop of green or blue depending on your preference and mix thoroughly and repeat as necessary. Prevent over colouring by adding only one drop at a time and recording the total number of drops per colour each time you add more
Use rubber gloves and an apron to prevent staining your clothing or skin. Concerning food colouring, it's easier to start with a lighter turquoise colour and add more drops as necessary than accidentally create an overly dark and undesirable colour.