The is at least one precedent for the sky blue - the underside of Spitfire fighter planes in WW2! (Admittedly possibly with a hint of green mixed in as well).

The is at least one precedent for the sky blue - the underside of Spitfire fighter planes in WW2! (Admittedly possibly with a hint of green mixed in as well). Link: https://en.wikipedia.org/wiki/Supermarine_Spitfire#/media/File:Spitfire_(At_Wright-Patterson).jpg https://en.wikipedia.org/wiki/Supermarine_Spitfire#/media/Fi...