1. recolour-mods: (a recolour and a mod at the same time..., not an object mod, a config mod or a global mod...)
http://www.modthesims2.com/showthread.php?t=179725
This recolour-mod itself has no graphical presentation or purpose on ANY host objects.
But, the presence of such material type and settings at the txmt of this recolour will make the host object to have the ability to activate the caustic animations of the pool-tiles and pool-wallpapers. The object itself has nothing to do with this mod or the animation activation but is just a vector instead. The effect of this mod will only affect the nearby pool-tiles and pool-wallpapers only, but not the whole lot or the whole game. If this recolour-mod is placed a few more grids away from the pool-tiles and pool-wallpapers, the caustic shader may still be activated, but the animation is not activated still. I can't explain why yet, or if any more other similar recolour-mods is possible. But, so far, this's how this instance works out.

2. Besides, I kinda believe sooner or later, custom material shaders will come to the light more. Yet, if a stand-alone one can be done, then they're not gonna be global mods but just additional mods to add material types, material effects and etc... to the game.

Still, I'll leave it open to other modding possibilities like lua and the layers.

Somehow, config mods are most likely global mods like the modded wall.txt or other modded scripts.

Thanks for all da priceless works... !