1. Dark brick and dark roof tile (which you can't see!)
2. in-out modelling of the facades/blocks
3. how the facades look a bit classical from one angle and a bit modern from another.
4. the concrete cills which double as little planters under some of the larger windows
5. white windows, panelling and fencing - showing that not all window frames need to be dark (although they almost always look better this way)
6.the slim strips of exposed concrete which i guess either are concrete lintols or an allusion to them
There are two other estates that I can think of which successfully combine dark brick and white windows. This one off the Peckham Road, below, which deserves a post of its own in due course.
The other is the Lennox Estate in SW15 which also has crisp concrete banding contrasting with the dark brick and nice proportions to the vertical elements. Images here, Will Faichney's excellent record of UK council housing stock + well balanced commentary.