Just to clarify the different colour variations, these descriptions were taken from the APHA website...
G Its Showtime defending his championship in Tobiano 3 year old & older geldingsTobiano - the dark colour usually covers one or both flanks. Generally, all four legs are white, at least below the hocks and knees. Generally, the spots are regular and distinct as ovals or round patterns that extend down over the neck and chest, giving the appearance of a shield. Head markings are like those of a solid colored horse - solid, or with a blaze, strip, star or snip. A tobiano may be either predominantly dark or white and the tail is often two colors.
Roses And Chocolate, sorrel overo, who took home All-around open horse, Super Gelding & High-Point English Horse at the World show this year.
Overo - the white usually will not cross the back of the horse between its withers and its tail. Generally, at least one and often all four legs are dark. Generally, the white is irregular and is rather scattered or splashy. Head markings are distinctive, often bald-faced, apron-faced or bonnet-faced. An overo may be either predominantly dark or white. The tail is usually one colour.
Tovero - Dark pigmentation around the ears, which may expand to cover the forehead and/or eyes. One or both blue eyes. Dark pigmentation around the mouth, which may extend up the sides of the face and form spots. Chest spot(s) in varying sizes which may also extend up the neck. Flank spot(s) ranging in size. These are often accompanied by smaller spots that extend forward across the barrel, and up over the loin. Spots, varying in size, at the base of the tail.
This whole blog post got started when I realized that Overo's completely dominated World's this year. At the World Championships I counted 4 Sorrel Overo, 3 Chestnut Overo, 1 Bay Overo, 1 Brown Overo and One Red Roan Overo that were all champions. There was a measly 1 Tobiano and 1 Tovero to round out the winners in all the different classes. Clearly you can tell where the trend in paint horse breeding is at the moment.
It's not like this is a new thing in the horse world, if you're buying a buckskin you can tack on probably around $500-$1000 more for the colour alone, possibly more depending on what discipline you are going into. However, I'm always amused at how many "plain-as-jane" sorrel's and chestnut's end up being championship cutting horses. There isn't any shame in loving certain colours either, I personally adore Tobiano's that are predominantly dark in colour, and as for Quarter Horses, of course I think palomino's and buckskin's are just "sooooooo prettyyyyy". It's just interesting to me the different colour trends that come and go in breeding throughout the years, and in what disciplines colour is an important factor, and which it doesn't matter much at all.