In the early Sixties, black was the most significant color for the Beatles. They wore black leather stage outfits, wrote the song  "Baby's in Black", and Paul even admitted "Our favorite colour was black" (Anthology, page 160)
But by the mid-Sixties, however, that changed. The spread of color television helped, and no doubt psychedelic drugs (which inhibit the brain's ability to process colors) played a role, as well.
In the late Sixties, though, that changed yet again - at least for John Lennon. Yoko Ono, whose color preference was white, gradually and progressively began to occupy Lennon's thoughts from their first meeting in November 1966 through the realization of their romantic relationship in 1968. She once created an exhibition of all white objects – including an all white chess set, accompanied by the instructions, “Play it for as long as you can remember who is your opponent and who is your own self.” Chess is a game of war – strategic war rather than violent war, but war nonetheless. Furthermore, white is a symbol of innocence (which is why brides wear white dresses) and in the context of war, white is the color of surrender – meaning the end of violent conflict. Yoko was a pacifist long before she ever met John Lennon, and in creating an all-white chess set, what she is doing is pointing out the fact that despite humanity's differences we are all human and we all share the same planet (just as all pawns, rooks, knights, bishops, kings, and queens all share the same chess board), and we all need to find a way to get along peacefully, i.e. without war or violence. She found a fresh way to illustrate the cliche "more alike than different" while simultaneously advancing her pacifist principles. How different, after all, would an all-black chess set be?
Yoko's influence on John Lennon - and particularly her affinity for the color white - is discernible as early as 1968. The album The Beatles is more commonly known as The White Album because of its stark plain white color with white embossed letters. How different would the album The Beatles be if its cover was plain black?
Moreover, there are a great many pictures of the couple wearing all-white clothing:
Additionally, Lennon owned an all-white piano - not coincidentally on which he composed the song "Imagine".
Beatles. The Beatles Anthology. Chronicle Books, San Francisco, CA, 2000.
This blog is a workshop for developing my analyses of The Beatles' music.