The Unicorn has green eyes and main camera. Banshee's are red.

I think you're probably referring to the Final Battle Banshee where everything turns "green", where in the novel the "green" psychoframe is actually described as rainbow coloured. Remember that yellowish-green aurora that pulled Axis away from Earth in CCA? That should be it, although it is visually depicted as bluish-green in the novel art and the MG kits follow this quite accurately.

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From what we've seen so far, the different variations and labelling of UC kits are:
Unicorn ver Ka - novel version, no vulcans, crap knee joints, pink beam sabres
Unicorn ver Ka Titanium finish - different paint job
Unicorn ver OVA - head vulcans + blue beam sabres, slightly better knees
FA Unicorn ver Ka - misleading nomenclature as it's actually a ver OVA Unicorn with the additional arsenal and green psychoframe
Banshee ver OVA - OVA version Banshee with fin funnel beam launcher + claw
Banshee Final Battle - Green psychoframe Banshee without OVA weapons

Out of all these variations, I think the Banshee OVA would be the best pick since 1) Banshee looks much more badass 2) You'll probably get the usual RX-0 weapons in additional to the OVA ones, more goodies = more fun

Now the interesting possibilities...
1) 1/48 Banshee head action base. Likely to happen since Unicorn and Sinanju already have them
2) FA Banshee? I'd hate to see this to be honest, since the FA setup is a makeshift configuration by the crew on Nahal Argama. EFSF shouldn't copy this design, but the OVA tends to change a lot of things from the novel so who knows?
3) For HGUC... almost every unit that made a cameo is going to be released in HGUC form... Juagg, Nemo... The new units that will be appearing the EP5 and 6 will definitely be released - Ankusha (meh), Rozen Zulu (another bigass HGUC), Jesta Cannon (guns guns guns !!), Hizack Custom (oooo the long barrel rifle...)

I'd be looking out for a Capule though...

And fck MG Duel is looking so good... and with the imminent release of MG Aegis some time down the road... Bandai, just take my money... just take all of them !