I knew just be reading the subject line that it involved red fading.
Here's your history lesson that I've shared a number of times (since most of you aren't as old as I am and were around back then!
In the late 70's, Red Dye #2 was removed from the market. Inconclusive testing determined that if you ate something like 500 lbs of it a day, you MIGHT get cancer, so they pulled it. There was no substitute that was as stable. Bright lights, sunlight will cause the reds of today to fade.
Purple = blue + red. Red fades, leaving only the blue.
Orange = Red + yellow. Red fades, leaving only the yellow.
Red fades to pink .... pink fades to light pink or even white.
Many CC'ers have said using milk instead of water in your icing helps stablize the color. Brands of color makes a difference. I use Cake Craft brand colors and rarely, if ever, have a fading issue.
BUt what you experienced is actually pretty normal.