For example, the original NES does not work with RGB, but with analogue NTSC signals, so an emulator has to do something to make the output appear on an RGB screen, and that implicitly involves colour-correction.
The SNES and Genesis do work with RGB, and the output is good enough to look reasonable on modern monitors, so most emulators would probably leave it as-is.
The Game Boy Advance works with RGB, but the built-in screen on earlier models was (as the article describes) low contrast, and games were made garish to compensate. Later models of GBA used better screens, and the GBA Player for the Gamecube output straight RGB to an ordinary television, so later games often used more sensible palettes, or even provided a palette option in the main menu. Thus, GBA emulators probably provide their own colour-correction, and almost certainly make it optional.