This is a modification of Gigatron 's NESify effect. It takes 16 user-defined colors and forces any other color to be one of these by checking the nearest color to it.
Do not mistake this with the "16 color replacer" effect! This one will force 16 colors in your game by comparing them to the nearest user-defined color. This means that, for instance, if your game has a certain shade of green and you define a different shade of green in the effect properties, it will change just fine.
This effect is NOT able to take a color (for instance, blue) and swap it with completely different color (for instance, yellow). For this one you'll have to use the "16 color replacer" effect.
Edit: (fixed link)
Link: https://www.dropbox.com/s/zo1wdkfaoipfd ... s.zip?dl=0
You can also use the Brightness property to make some cool fade-in/out animations while still forcing your game to use limited colors: