When I was growing up, my mom always had Wilton gel food coloring that you had to dig out with a toothpick. I hated it. I found it messy and annoying and the red was never red (come to find out, I was actually using pink!). Anyway, time went on and I became and adult and I bought myself food coloring from the grocery store with the little triangle tops that I could squeeze 1 drop or a hundred but didn't have to use a thousand toothpicks to get the color I wanted. I thought these little squeeze bottles were the pinnacle of food coloring. How wrong I was.
Fast forward a few years and I took my first cake decorating class. In that class I learned about different types of food coloring. The water based food coloring I had fallen in love with had a thousand flaws. Well, mostly just one. It was too liquidy and would change the consistency of my frosting before I could get the right color. Enter, the dreaded gel coloring. Gel coloring gives you bright, deep color without watering down your icing. So what kind of food coloring should you use for your project? Good question.
Gel Food Coloring: The two brands of gel food coloring I use most often are Wilton and Americolor because that is what I can find in the store. Wilton comes in little tubs while the Americolor comes in nice little squeeze bottles (no toothpicks!) I have heard that the no-taste red is superior in the Americolor, so that is what I use. Gel food coloring requires less color than water food coloring and does not thin out the frosting. Tip: gel food coloring gets brighter/darker with time so color your frosting (or fondant), wait 15 minutes and then evaluate if you need to add more. I learned this the hard way with my sister's bridal shower cake and she had very dark pink roses on that cake.
Powdered Food Coloring: Most often used to make French macrons. Powdered food coloring does not add any liquid to the product and is best for projects where you have no leeway with the amount of liquid in your finished product. I have never personally used powdered food coloring, so I cannot attest to its attributes.
Oil Based Food Coloring: used for coloring chocolate. Chocolate will seize if it comes into contact with water so the gel food coloring doesn't work. (If you have never had chocolate seize on you, count yourself lucky and just trust me on this one).