1991 Explorer Stereo Help

I just purchased a new to me 1991 Ford Explorer a few days ago.  It has a stock stereo.  I tonight bought a Kenwood CD player, and went to install it, but am having problems figuring out what wires are speaker wires.

There were two harnesses going into the stereo, a main harness, with the power and lights and ground leads etc, and another harness, which I assumed was for the speakers.  The wires in this second harness are very small, and were in an insulated wrap, with a silver foil around them.  I did a search on this website and found a quick wiring diagram for this vehicle here https://www.the12volt.com/installbay/detail.asp?info=alarm&year=1990-91&make=Ford&model=Explorer&ID=17794&type=Stereo  The wiring colours are totally different.  The plug I have has the following colours : 

Green, WHITE/ Orange, Blue/Black, Yellow                                                                                                            WHITE/ Red, Brown, WHITE/ Purple, Blue.

I am totally lost here, can someone please help me out?!

had this same problem if u wnat to uses the factory amp go to ur local walmart or w/e and by the plug ins the make sure u run the factory turn on with ur turn on form the deck

Going by the wiring diagram link I listed above, would that be the amplifier remote (Blue) wire?

Also, I bought a wiring kit when I bought the stereo, but it only had the main plug, not the little one I assume is the speaker plug.  In the main plug, the ground from thew stereo isn't going to the black wire in the stock harness, it is going to a red wire in the stock harness.  This doesn't make sense to me.  The stereo does turn on though...and appears to work.  This red wire isn't even listed in the wiring diagram I have the link to.  Is there possibly more then one wiring diagram?

No the diagrams just never mention the red wire, it is the ground, don't ask it's a Ford thing, some years it's black w/green others it's red.  If you just want to wire directly into the amp get an Metra 70-5511 harness, if you want to wire in to the amp properly you will need to get a high-to-low level converter designed for the Ford plug, any stereo shop should have one.  If you want to actually use your radio power then you can use the wiring diagram you have but you will need to bypass the stock amp, which is in the rear right side panel of your Explorer.  Hopefully you have a four door and the sport 2-door model is a pain to take the side panel out of, also be careful of the clips around the rear window wih the age of the car they are going to be very brittle.

Well, I dunno...I put the auxilliary power lead (from the CD Player)  to the amp, and found I have speakers.  Makes sense so far?  Now here is what confused me.  There were eight wires for the speakers, 5 speakers, (Though the one in the very rear of the truck seems to be a sub?).  Anyways, I started touching speaker wires from the stereo to the ones in the truck...if I touched one lead, either positive or negative to one of the speaker wires, the speaker worked.  I started with the right front wire, and found the right front speaker...actually, I found two right front speakers.  One being a mid one a tweeter perhaps?  I dunno.  I found there were two wires per speaker corner, and if I touched one wire to the power speaker cable, and one to the gorund speaker cable, it sounded great, two seperate speakers in each corner working....Is this normal?  Shouldn't there be a positive and negative for each speaker?  Since it works, I left it as it is, but is this wrong?  Will I have problems in the future?

Thanks for the help all who replied here!