On Cato wearing a black toga ... this appears to come from Plutarch's life of same (via the Internet Classics Archive):

And in general Cato esteemed the customs and manners of men at that time so corrupt, and a reformation in them so necessary, that he thought it requisite, in many things, to go contrary to the ordinary way of the world. Seeing the lightest and gayest purple was then most in fashion, he would always wear that which was the nearest black; and he would often go out of doors, after his morning meal, without either shoes or tunic; not that he sought vain-glory from such novelties, but he would accustom himself to be ashamed only of what deserves shame, and to despise all other sorts of disgrace.

... note in passing: Cato didn't have a tunic on under his toga.