Most everyone at one point or another will use food coloring in their cake making. Some use natural colors such as ones from Color Garden or India Tree. I personally have not tried these. However, I have made my own colors using beet juice to produce a pretty pink, tumeric to achieve yellow, blueberry juice for light purple and spinach juice for light green. It wasn't really difficult but it was time consuming. The customer had a child with severe food allergies and could not have anything with dyes. So I made everything so I could control what was in the cake. Have you tried using natural food coloring with good results?
My favorite colors are by AmeriColor. These are food gels and give the best results for true colors. I would recommend trying a student color to see which colors you use the most and then purchasing a larger bottle of that color. Some colors you will not use very often and they can go bad. They don't spoil, but the gel can separate over the period of a few years. I learned this the hard way when I found a bottle of soft pink that had been opened and pushed in the back of my drawer. I squirted a little into my frosting and it caused a the worst streaking I've ever seen! I realized after the fact that the gel had separated and congealed. This bottle was 5 years old. I've never had it happen before or since then. Lesson learned. Use up your gels!
One product I have not been happy with are colors from Sunny Side Up Bakeries. I have purchased these from my local Hobby Lobby store. They no longer carry the AmeriColors and so I bought this as a substitute. I have found the Neon Pink to be very runny and the color streaks. Have you tried any of their colors with good or bad results?
This is from my personal experience. I have not been paid to advertise for these companies. The above links will direct you to my Amazon account. If you would like to purchase the colors through the link, my family and I will receive a small commission from Amazon.com. Thank you!