First:
You need a working ENBSeries (tested with up to v.75), an active reflection in ENB, TXDWorkshop and some painting program 
such as Paint, Photoshop, Gimp, else.

Second: the effects, which shall be talked about here, works by a bug in ENBSeries, as Boris stated. 
So maybe it will be stop working on later versions (last tested: v.75). Its not a bad bug, its a good bug somehow.

All these effects work by moving in the lights, depending on what angle light falls on the vehicle, the color differs.

There is a rule: use a light and a dark color. The light color will be made via Paintjob, the darker one via Primary Carcolor (Transfender, else).
Open TXDWorkshop, load any vehiclename1.txd (or xxx2.txd up to 4). In there you will mostly find one picture. Extract it, and open it with any painting program. 
Now make a choice: which color should light through the darker one? I made the experience, bright neon-like colors work best. 
You can use stripes, geometrics, whatever. Once you have finished your work, think about filesize. 
A one-colored painting doesn't need to have a size of 1024x1024 and 300dpi, 256x256 and 70dpi mostly are enough. It does no quality drop, but a better loading GTA SA. 
Its up to you, and how complicated your work is. Of course, with a fully painted Paintjob, pictures and more on it, such a small number of dpi will look shitty. 
Think about it, always make a choice depending on needs and cans.

Now import your artwork while having the entry in TXDWorkshop marked. The one entry which is marked, will be the one which is replaced (important if there are more than one entries).

Save/close the file and throw it in your gta3.img. Get your car, go to Transfender (or else) and now listen carefully: first buy the paintjob you just have made, after that choose a primary car color. 
ENBSeries have to be activated to see an effect.

In TF (..else..) yo will notice the different colors hardly, but if you drive the car into the sun, you will see a huge effect, depending on which colors you have chosen. 

http://s1.zetaboards.com/Kottons_Chop_Shop/site/