Batman Kerb Drill Advert 1966

[The Dark Knight]

The timeline colors presents is indeed brilliant because it makes logical sense. It's the TDK Returns theory in reverse - that Batman started out optimistic but time turned him into a terse, aggressive warrior. I will add that perhaps West's Batman evolved into a detective over the years (and less of an angry brawler) due to the threats he faced. He had to use his brain to solve riddles and decipher jokes, and the addition of Robin helped him a great deal in this regard.