1994 GMC Safari starting problem

I have a 1994 gmc safari van rear wheel drive. Just recently I run into a problem with my starter system when I turn the key nothing happens the van does not start and the starter does not turn I have had the starter checked and it is good, there is a purple wire that attaches to the starter and someone told me that it should have power when the key is turned to the start position but there is no power there so I have narrowed the problem down to that but the problem I have now is that I don't know where that wire goes to and I am not able to follow it along to find where it goes Can you help? Or if this is not right please let me know what else it could be. Thanks