Couple things....
I did see that little tiny tab between the blue and green plugs. I tried to pull it back and move the plugs, but it would not budge. I felt like I either wasn't getting the tab pulled back properly or the force was not enough. I thought I'd need some pliers to grip it. I can try that again.
Also, I do have a CD changer and factory amp.
I found this, but I'm still not sure how this would work.
AUX-BKR Auxiliay input Jack for Select Becker Radios with CD Changer :: Auxiliary Input Adapters