my favorite color way is still the USO. although two colorways that i think are greatly under-appreciated are the AO and the OG.
the AO colorway got a lot of flack initially. i even thought they looked quite floppy in the first set of leaked photos. to see this shoe in actuality however is a completely different aesthetic. all three colorways that came out prior to the release of the synthetic leather shoes were great IMO, but, in particular, i liked AO colorway's balance between grey and white in the upper, setting the ground for the volt and red.
The simplicity of the colorway in the OG shoe really brings out the subtleties of the shoe's design. the TPU frame, adaptive fit system and mesh upper all being one color has a really nice effect, highlighting the form of the adaptive fit against the mesh. it was also the first release of the year featuring a TPU frame that matched the color of the upper, much like the previously leaked but later released USO colorway.
EDIT: one reservation i have is not necessarily with the shoe but with the rest of the OG outfit federer wore with the shoe. i feel like the shoe would look great if the entire outfit werent comprised of white and red.