It adds different coloured rats to the creature leveled lists.
White rats will mostly only be found in Vivec.
These have evolved from escaped pet rats and are a bit stronger than other rats.
Although all these rats are very slightly stronger and quicker they are by nature more docile...
unless diseased or blighted of course.
Only blighted black rats added in the Red mountain region
Only grey and black added to caves
Brown and tan in the wilds except in Molag Mar, Sheogorad and Ascadian Isles areas where you may find only grey.
you will also find more grey rats around the port areas and in ships holds.
Rats have also been added to most towns and villages... their colour will depend on the area.
This will also replace individually placed rats in game with a new rat leveled list which can be any colour...
There is alway the chance you will still only see the existing rust rats though.
You will now of course see more rats... but not to many :)