White Factor
Gene Fundamentals
In real life the amount of white a horse shows is controlled by a complex combination of its base amount of pigment (how much eumelanin and pheomelanin it has) and all the genes that cause normal pigment production to fail. The more white spotting mutations a horse has (like splash, roan, tobiano etc.) the less pigment is created and the less pigment there is to push against white areas. In the game this is simplified to a numerical value and listed as None, Minimal, Light, Medium, Large or Extensive.
In the future White Factor will be replaced with more accurate calculations based on pigment.