Although we register our mini's as pinto, the specific pinto pattern we are referring to is actually Tobiano. 

If you look at a pinto society, that registers horses based on colour and background colour (pedigree), you will see they accept overo patterns as well as Tovero patterns.

The Tobiano pattern is caused by a dominant gene. At least one parent must be pinto to give a pinto foal.
To get a homozygous Tobiano both parents must be Tobiano. 

The amount of white in the coat pattern is not a reliable way of determining whether a horse is homozygous or not, as very minimal homozygous Tobianos certainly do occur.

• The white on the body is arranged in a vertical pattern and will usually cross the horses topline somewhere between the ears and tail. The spots of a Tobiano are a rounded shape with clean, sharp edges. 
• The tail can be two colours but the colour will be at the bottom and the white will be at the top. 
• Occasionally horses with the tobiano gene do not have any body spots. These minimally marked horses will have white leg markings of varying size. There are even horses who have only a couple short socks that test homozygous for Tobiano. These horses can and do go on to produce Tobiano offspring as reliably as any other horse with the Tobiano gene.
• You can have a blood test done to test if your horse is homozygous pinto.

Many people think Tobianos with  white face markings or full body white usually have at least one other pattern in addition to Tobiano. 

• The heads of Tobianos seems to the be the last part of the body that is covered by white so you may see some Tobianos with all white bodies and coloured heads. 

• One characteristic of Tobiano is colour on the flanks and chest, usually called chest or flank "shields". 

• Small spots of colour commonly called, Ink Spots, Paw Prints, Cat Tracks, etc. These small spots occur in the white patches anywhere on the body of the horse, they are usually small, round and occur in groups so they are easily seen as different from the larger patches of colour that makes up the Tobiano pattern. These spots are the same colour as the other coloured parts of the body. 
  This marking is associated with homozygosity of the Tobiano pattern but DO NOT necessarily mean that the horse is homozygous. These spots should not be confused with the Appaloosa pattern mixing with the Pinto pattern(s) and therefore causing a "Pintaloosa".

• On some Tobiano horses the pigmented skin extends a short way beyond the patch of colour into the white area. The result is a shadow or halo.
  Best seen in clipped horses.

• Another characteristic associated with the Tobiano pattern are ermine spots or distal leg spots. Ermine spots are spots of colour in the white close to the hoof. Distal leg spots are spots of colour that occur in the white on leg above the ankle.

• Another trait of Tobiano that occurs on the leg is spots of colour around the chestnuts, on a leg that is white in this area. Shown below progressing as the colt ages.

3 months	6 months	12 months

you can have your horse lab tested to confirm if it is homozygous. 
UC Davis is one lab that provides this test. The homozygous pinto test requires a blood sample.

  >> Examples of Tobianos

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