Welles probably felt more comfortable with Black and White; his was to some extent, an art of light and darkness. But personally, I'd like to see more Welles in color, and hopefully we will before too long. Several of the works from Welles' "color period" remain unseen, so it's hard to judge exactly what his full acheivement in this regard was or would have been. Apparently, THE BIG BRASS RING was to have been in black and white until the climax of the story, during which a fireworks display would have been in color. I'd like to find out what that meant.
There are also a few fascinating snippets of color footage in the IT'S ALL TRUE docu, including that great "West Side Story"-like recreation of an old-time Carnival street fight. If Welles' Brazillian adventure had turned out better, maybe we might have had an Orson Welles color period much earlier in his career as well. It's interesting though that, 20 years later, his first color feature THE IMMORTAL STORY was quickly followed by an abridged version of THE MERCHANT OF VENICE which, from the available fragments, seems to have a strikingly similar look and atmosphere to it. Perhaps Welles found his color vision quickly, but after a few films felt he had nothing left to prove in color. Not that he had anything left to prove in black and white, either.