Nissan Stanza Radio Install Problem

I was installing a Cd Player in my friends 91 Nissan Stanza, it already had an aftermarket tape player in it, but when we removed it, everything was messed up. Whoever owned the car before him had removed the factory radio, cut the harness, added new wires, and duct taped everything together, even the pocket was duct taped to the radio.(Yes duck tape not electric tape) I traced the 2 main(Ignition and Battery)  wires to the tubing in the dash and connected them to the radio, turned the ignition and the radio did nothing. That model doesn't have a ground wire to just hook up, the old radio was grounded to the side of itself, we tried that with the new one and nothing, we grounded it to screws, and thing above the ash tray that looks like it has a main grounding wire on it, and even cut the ground to the cig lighter and tried it and still got nothing. Did I ground it incorrectly, or is it a power issue? The power wires back there are so messed up, its flustrating. The Constant 12v for that car is suppose to be RED / Black, but it looks more Red with blue dashes on it.

 

Could I buy a multimeter and test the wires, if so, how would I do that(I never used a multi before)

Its a brand new radio so it should work, is it dangerous to test the radio on a battery, the radio wires are fused already.

 

Any help appreacated