Similar thing was what inspired their whole name switch. Back in 2010 when I drew first illustration, I wanted to write the name of Black over his white clothes (wasn’t named yet) and wanted the fastest way to write it without strokes, shadows or styles for it to be visible, so I had to use black text and used the opposite for White, which made me go, ‘oh why not?’
Then the plot and their personalities seemed to fit the idea born from mere laziness.
(I struggled much while writing today, so it’s aren’t my thing today apparently. I hope the above makes sense lol)