That's better than plain text that just happens to be a hidden control, but text with a background color might just be... text with a background color, for emphasis. Or it's text with a background color, to distinguish it from editable text. A background color does not tell the user that it's a control.

A box around it? Slightly better, but still doesn't convey state. Sure, you can fill it in when it's "on," but that's still guesswork on the part of the user if he arrives to find it filled in already.