Never trust the colours ...
There is always the possibility that someone ignored the "scheme" and wired it up, pin-for-pin correct using whatever they felt like.
My wireless mouse has a black wire for battery + and a red wire for battery -
The connector on the board has black to "+" and red to "-", and it's polarised so nothing can go wrong.
Other than using the wrong colours
You need to probe the Microusb pins to see if you have continuity.