The most egregious example is old CGA games that were written to work on composite monitors. Without the composite display, they appear monochrome or cyan and magenta.
https://user-images.githubusercontent.com/7229541/215890834-...
It blew my mind when I finally learnt this, as I spent years of my childhood playing games that looked like the examples on the left, not realising the colours were due to the RGB monitor I had.