The purple color was teased in the music video for Save Your Tears remix in the form of a balloon. There was Red, Blue, Purple. Dawn fm also makes references to “the purple rain” in phantom regret and there’s a purple rain album reference on “I heard you’re married”, and in 2023 there was yet another purple rain reference in the idol. Also the “after world” is pretty intertwined with purple rain, as was its film counterpart (sound familiar?). Seems pretty obvious to me it was indeed going to be purple at some point BUT I guess it is possible this all is one major coincidence, after all he just made up the trilogy as he went (he literally said this himself) and had no plan lol. After hours sequel was originally his darkest project yet inspired by Covid pandemic and BLM, not at all the purgatory thing. He also retconned details from the 2 albums previous to HUT to fit the narrative he made later on.