I feel like the deal with Gaster's door in the 10th Anniversary Livestream isn't a "COPIES ARE MONOCHROME" moment where Toby's copy is the "original" world, its instead "BUT YOU COLORED EACH OF US IN WITH CARE," our love for the fun event and us trying to figure who the "mystery man"/Gaster is is why the door is colored in. It's a reflection of how much the fandom was able to turn this one little secret into something grand.