If California regulators get their way, auto makers may soon be forced to rewrite a cliché from the Ford Model T era and start telling customers they can have any color they want as long as it isn’t black. Some darker hues will be available in place of black, but right now they are indentified internally at paint suppliers with names such as “mud-puddle brown” and are truly ugly substitutes for today’s rich ebony hues. So buy a black car now, because soon they won’t be available or will look so putrid you won’t want one. And that’s too bad,...