Originally Posted by Mr_Fixler
Not so much, actually.
What he did denied millions of humans the chance to live their own lives, and he denied humanity at large the opportunity to evolve on its own, even if it resulted in a nuclear war. He decided humankind could no longer be left to its own devices, and that it was up to him to achieve order - at any cost.
So yes, he did adopt Black. Black achieves its goals at any cost. But he didn't renounce White, on the contrary. White values - order, peace, working together - are at the core of what he hoped to achieve.
What he took away was the ability of millions of human beings - and humankind at large - to evolve, to grow, to change, and to live lives of their own making. Live according to their own natures and impulses. All of that was replaced by artifice and deception.
You know what color that is anathema to? Green. Green abhors treachery, deception, and the unnatural. Ozymandias didn't turn Sultai - he turned Esper. He had completely lost faith in humankind itself, and turned his back on it - even with regards to himself. It was not in his nature to become a mass murderer - he was a kind man who genuinely wanted to help. It was White idealism, Blue scheming, and Black amorality that turned him into what he is at the end.