We love our cannas and have 3 different colors of a variety that we really like. Our understanding and what we think has happened before is that if you mix the colors they will bloom what they were the first year but will gradually all go to the dominant color. (usually yellow). Is there any truth to that? We have a nice deep red, a yellow and an orange mix with variegated/striped leaves. I would love to mix them in our long flower box but I'm nervous.
Yes, Canna Lily can make color mutations, this is often how some colors are 'born'.
Not every plant will do so, but if you grow Canna long enough you will see this in your garden.