Dirtyderv

Hi guys I have a 2004 c5 diesel, I changed my head unit over to a pioneer one last night and switched the ignition off and stereo stayed on. I've tried swapping the red and yellow wires over but to no avail. Any help would be grateful. Thank you in advance

Good morning guys and girls. I've recently bought a C5 and thought I would join the forum as this way j can get to know abit more about the car that I have bought and pick your brains if I need any help along the way. The car I've bought is a 04 plate C5 2.0 hdi VTR. So far I'm impressed with it but only time will tell if it's as good as first impressions