“One day I decided to see what the kapton tape I use for my 3D printer bed looks like when applied to the display, and to my surprise it turned out great, transforming the boring regular LCD into a nice amber color.”
A strip of 3D printer tape turns a cheap Casio LCD amber. Other polyimide tapes give other colors, as long as they are thin enough. The watch is decades old, cheap and fully hackable with household parts. Try doing that to a smartwatch.