I am doing a similar thing.i am in the process of buildin an Ultramar PDF army - 8th regiment( i konw Ultramar isn't a planet but it has a nice ring to it).
Basic main colour Scheme is -
Astronomican Grey for the fatigues and vehicle base colour.
Mordian Blue for the armour and picked out areas on vehicles.
Charadon Granite for boots and weapon cowlings.
I am using up all my old Ultramarine Transfers i have collected form my 12,000 point Ultramarine army that have never been used.
It being the 8th regiemnt it allows me to use the scuplted Cadian banners with a bit of filing.
i would post photos but my digital camera is playing up.