NSM Firebird (ES-IV) Wall Mounted CD-Changer questions

[BigBird0000]

My first post on the NEW server!

I have a few questions about a Firebird (ES-IV) juke that I am working on after letting it sit 4 years in my garage.

1) Is there a way to test the audio out from the cd-mech (the 4 pin cable that goes to CENTRALE TB CD). I just want to see if the amp and or CD are working are broken.

2) What cassette and CD trays do I need? The label on the CD-changer says

"CDM 4/36 DRIVE  nur (just for) ES-IV
   ATTENTION: Blue Cassette Only"

I have seen videos and pictures of the Firebird, and the Cassettes don't look blue, even though I can see the "Blue Cassette Only" label on those pics.\
What does the "Blue" really mean... what cassettes can I use? Are the CD trays for the NSM jukes all compatible?

(When I got the juke, it was missing Title Indicator II Card, Controller card, no CD cassettes or trays... so I am kind of going in blind here.

Thanks for your help!