I don't think colour has anything to do with why this went wrong.
"we had a fwb situation for a number of years"
"So why do I hate myself so much".
You already know the answer, though hate is such a strong word one that I won't use. If you don't love yourself, how are you expecting to find someone that will love you?
You went into it knowing it was fwb but hoped it would turn out to be more.
You are angry at yourself, for allowing it to go on, and on, and on, and on into years . Angry at yourself, to have gone back after dusting yourself of only to feel worse and walk.
Go seek help to do that.
Then you will find love in return.