That brown “oxidation” look on the joints and connectors made out of steel... “nature’s modification”... especially on chains!
Those stupid silencers that have a blue colour that makes them look like they have been very hot. And coloured nuts and bolts.
That picture reminded me , super modified chopper's with ridiculously small capacity fuel tanks ! Even at 60 mpg they'd have less than 80 mile range between fuel stops !