Long post ahead!
So if a fairy's pallet changes, it most commonly happens around enchantix because of how inherently traumatic the concept of self sacrifice is.
Flora's colors would dull a little, nothing major but the pinks would look more "aged" as a mental reference to the black willow's time affiliation.
Musa's also are not a huge change, mostly a slight darkening as a symptom of the pain she went through when her wings were shattered (also might be a reflection of the darcy/stormy dynamic and how musa relates to both of them in different ways but she's not ready to unpack that teehee)
Tecna's is a more dramatic change due to the prolonged survival state she had to be in while trapped on Omega. She used her transformation to survive until she was able to scavenge parts to build a warming suit for herself which meant she drained her magic every transformation (via exploring and setting up a safe camp warmth bubble). Every transformation ended up lighter and lighter as a camouflage against the ice-snakes and the thawed prisoners. This would be a more permanent color change, probably only darkening a little as she healed, especially because tecna doesn't base her identity in being a fairy so it wouldn't cause her additional stress.
Stella's colors would mostly shift after earning Onyrix. Stella had the most negative reaction to her nemesis out of all the winx and the episode continued to effect her for several weeks after it was done. However, due to this episode, she did gain a much more balanced look at her sense of self worth, acknowledging that she has bad days and needs to treat herself with compassion instead of catastrophizing. In a way Stella's colors changed not because of trauma but because of growth.
Oh girliepop. Aisha's color change is a pure grief reaction to Nabu's death. It's not a permanent change, because Aisha would come to associate the darkened color with feeling shitty and the longer it stayed dark the more upset she would be (she had a few ups and downs color-wise along this timeline, its not strictly linear). It also wasn't a thing that happened to "her" like, Nabu dying was definitely traumatic, and similar to daphne who had grief involved in her color change, but daphne also underwent torture and other losses of autonomy that left lasting physical symptoms, which is why her color change was permanent.
Bloom has a few changes (because of course she does). Dark bloom dimmed her colors in season 2/3
Bloom's incomplete enchantix highly saturated her colors, and her complete enchantix settled into a slightly more blue tinged set which is permanent.
not so much an actual color change as an affliction, but I thought it would be fun to include. Fairies in core fatigue have scattered, shifting colors and design elements that bleed into each other.










