[nine_k]

The video shows us the wreck site at the end. The rocket is mostly one piece though damaged by hitting the ground too fast and from a (relatively minor) explosion.

It must be possible to find most pieces, and certainly check the engines, even deformed, for overburn signs.

[grey-area]

Bright green flames at the end is a giveaway of engine-rich combustion.

[mhandley]

Indeed, which in turn is an espected outcome if the engine is running oxygen rich, and hence much hotter than the design point. Pretty likely the low fuel tank pressure was the cause of this, and I'm sure SpaceX will have the telemetry data to know for sure if this was the case, irrespective of what pieces remain after the landing.