Metra adapter has the connections printed on the wire, hard to go wrong. Most HU have the I/O right on the unit itself.

 

Not knowing what adapter harness being used, among other things, here is what I suggest. Follow the stock wire through the adapter and connect to radio using diagram on radio. Basically disregard the adapter colors and follow each stock wire through the adapter into radio.
Use the link I posted earlier for stock wire functions and their corresponding color.