...back to the beginning...alfa have changed the +12V constant and +12V switched/ACC wires around. these are wires 4 and 7 in ISO plug.
not only that, the factory alfa headunits can be turned on without needing the ignition key because there is no 'ACC' setting on the ignition.
back to complete basics, a NORMAL (non-alfa) car would be wired:
*wire 7 in ISO plug would be +12V 'constant' and should be matched up to the yellow wire on an aftermarket/pioneer HU; this wire provides the main power source to the unit
*wire 4 in ISO plug would be +12V 'switched/ACC' and match to the red wire on an aftermarket/pioneer HU
*cannot turn the HU on/off without the key; also means HU automatically turns off when you remove the key and leave the car
*turning key to ACC (or ON) activates wire 4 to trigger the HU on/off
in an ALFA, the factory HU is wired:
*ISO wire 4 is now '+12V constant' (always has power)
*ISO wire 7 is now '+12V switched/ACC' (has power when key is at ON)
*BOTH the red and yellow wires (or the equivalent) on the HU connect to wire 4, making both always have power
*as such, HU can be switched on/off regardless of key position or having the key at all
now......you have to decide how you want the pioneer HU connected:
1. like alfa-factory, being able to turn on/off regardless of key: if so, connect BOTH the pioneer red and yellow wires to ISO wire 4 which is the RED one on the adaptor plug; like your last pic
2. like non-alfa cars, having the HU turn off automatically when the key is removed, and not being able to turn the HU on without having the key at ON: connect the pioneer red wire to ISO wire 7 (yellow), and pioneer yellow wire to ISO wire 4 (red)...this is what you have shown in your first photo
easy to be confused cos alfa have done their best to confuse the world by not conforming with ISO practises.
other 3 plugs:
*yellow: blaupunkt lowlevel audio output and amplifier remote output wire
*green: mobile phone handsfree kit connector
*blue: CD changer, data bus (trip meter info); i think this has steering wheel control wiring too