You simply add the .package files to your mods folder as any other Custom Content, and remove the files to remove the effect.
The result will look different depending on what EPs you have. For example, there is a City Living Oak tree which overrides the colors of random oak trees in most worlds.
Forgotten Hollow, Strangerville & Evergreen Harbor are least affected, but I might make add-ons for the last two.
96 items sounds like a lot, but there are sooo many objects and plants in this game, it will still be a balanced mix of normal and pastel, and green trees and pink trees.
Tested in spring and summer.
Recommended: ‘basegame’ file + every EP you own! The more the better (^.~)☆
I wasn’t sure exactly what to call it (Pink World, or Kawaii World also came to mind, ha ha), but Pastel World seemed most descriptive (^-^*) The look is quite different depending on where your sim is. My favorite is Britechester, but I also like how Sulani is more dark pink and cyan than the others.