Red is the hardest color to use. I have found that adding some coloring to the butter as you cream it helps to get a base without using as much. Then, after you have beaten in the sugar and milk/water, you can add more to bring it to the shade you want. Also, make sure you add a flavoring such as vanilla or any other extract to offset the coloring taste. Here I don't worry about using a clear vanilla because the darkness of regular vanilla actually helps deepen the color (but don't go overboard on the vanilla).
This works with gumpaste for flowers as well. I use a powder mix and I add coloring with the water as I measure it and it gives a nice base to work with, without making the paste too sloppy.