Colour changes in my Axolotyl females housed together continued

Hi everyone, I recently spoke about my wild type female changing colour until she lost all pigmentation and became indistinguishable from her dirty Lucy sister. At the time their tank was in a bright sunlit room and the temperature was at the top of their comfort zone. The colour change occurred within around 8 weeks or so. No other signs of illness. I then changed their location to a dimmer cooler room and now her sister has developed pronounced dark facial spots/large freckles. She has however remained Dirty Lucy in colour. I am wondering if the colour changes could be due to temperature. It occurred to me that perhaps Lila was feeling heat stress more due to the dark pigmentation of her skin and became white as it reflects light and therefore would cool her better. Now it's cool maybe her sister Spook, is gaining darker spots for the same reason? Just speculating but has anyone any ideas about this? Oh they are now 3 years old so nothing to do with natural changes as they become mature.