I've noticed when I incorporate real butter into my BC I have color change issues. One example is when I was piping stars on a cake and went to refill my bag the new stars were coming onto the cake in a different shade... I asked my instructor about it when I was still taking classes and she said I must not be mixing well. I'm absolutely positive I mix well. It only happens when I incorporate real butter into the icing. If I use 100% shortening I'm good to go, but I really prefer the taste of the butter... What am I doing wrong?
Some colors intensify as they dry and some fade when they come in contact with light (sun or lightbulb)
I have had lots of issues with americolor. Especially the dark blue, pinks and reds. You may try a different brand or type (like powdered)
Sorry I cannot answer your question scientifically. Maybe someone else might have a better answer.
This is common. If you make up your colored icing at least the night before the color will have time to 'deepen' and you should not have as much a problems. Also this usually happens to people who have hot hands. Keep a 2nd bag all made up in the frig so you can change when ready w/o the color change happening.
My icings are mostly wilton icings. I've used some Americolor and I've also used the powder with my blues and reds. I've had the same thing happen each time...