Someone in the Ella's Garden cubit had pink mums that changed to yellow while growing in a pot. I guess they can change. I wonder if it could be temperature or pH dependent? Do you think the growers add dye to increase sales? My mums simply disappear.
Your roses look so healthy. I have been trying to companion plant instead of mulching, but I am fighting weeds. (I am also playing the is it a weed/is it a plant game.)