Why do colo(u)rs look washed out on some GB emulators (i.e. no$gmb, etc) but not on others ?
This is because code has been added to in order to do “colo(u)r correction” . This “correction” code creates washed out colo(u)rs to better simulate how the game appears (or would appear) on the real GBC hardware. Often, GB emulators (such as no$gmb) have a configuration option to enable or disable this “auto correction” feature. The consensus seems to be that greens and blues reproduce well on the GBC but the reds seem to be faded.