Is there a guide on how to change the effects?
What do you mean by "change"? If you mean recoloring to colors that are not affected by the color overlay parameter, then it can only be done by editing with any hexadecimal editor! The effect itself is an internal Nival format; I haven't been able to find a plugin for exporting from Alias Maya 6.0 yet, but that could change...

---------------------------------------------
Неудачное планирование ведёт к неудаче ...
NCF - мод, добавляющий дополнительных существ в HeroesV 3.1