First, you got to be cautious, since connecting things wrongly might fry the ports and render them permanently unusable.
Now, that said, NORMALLY when you have these wire colors, then red is +5V, black is ground, green is D+ and white is D-.
You SHOULD however check with the case manufacturer, or measure what's what by measuring what wire connects to which pin on the front USB (with the latter's pinout in hand of course).
regards, Peter