a config option to customize the colours of the eyes, or their effects, would be very cool! adding the ability to have effects like wither, nausea, instant damage, bad luck, etc, or maybe even an option for randomized effects could all add to the spookiness.

I am attempting to do so with new sounds. What is the folder nesting address for the assets, their filenames, and how do you include a randomised script for appearance/image files? Do you have links to existing respacks for this specific mod? Have you done it?

look into optifine mob variations for that, as they contain mob variation built in. the assets are in the eyesinthedark/assets folder

Hey, know I'm a bit late on this (I'm not the mod creator, just a fan of the mod). But you can change the eyes to your hearts content through a resource pack :)