Classic paint

What I consider the classic paint genes are tobiano, frame (lethal white overo), and splash.

Now... the APHA would probably sort of disagree with me, because they include sabino (which I'll cover with the roaning patterns) and generally frames all colors as tobiano or overo (with subvariations of splashed overo vs frame overo vs sabino overo).  Or tovero, which... is not a thing at the genetic level; it's just tobiano plus an overo pattern.

White patterns will almost always have pink skin underneath them, which can make it fun to give a grey horse a bath sometimes.  :)  Sometimes they may have edges where the normal dark skin extends under the white, which produces a look that is apparently highly desirable in the model horse customizing craft community.  (Another random thing that I have knowledge of...)

Also of interest, if you've ever picked up a horse book by a British author (I plead the fifth on how many horse books I have, by the way) - the terms piebald and skewbald just refer to black-based pintos (piebald) and pintos with any other base color (skewbald).

And a tri-color pinto?  That's actually a bay, unless your horse has a chimeric mutation.  Chimeric mutations are when a horse had a twin while in the womb, and the two merged during development.  That's what gives you things like brindle horses (some of which are so neat to look at) and horses where part is black and part is chestnut.  This link has some cool examples.

So let's talk tobiano first.  Tobiano is dominant, so you only need one copy to see the pattern.  The edges of the white are smooth lines, not jagged - like drawing a curve vs. drawing steps.  The horse's head is generally dark with minimal markings (blaze, stripe, star); if they've got a flashy head, chances are they've got another pattern gene causing that.  In general, it's a vertical pattern - it crosses the back and tends to be very up and down along the horse's body.  I've seen it described as oval, but I have a hard time seeing that on most horses

These two are awesome examples of tobiano (from a local show).

White from the knees and hocks down is pretty commonly a tobiano thing, as is white crossing the back between the withers and tail.  Tails may also have white in them.  The chest and flank both tend to be dark, as well - sometimes the dark on the chest and neck is referred to as a shield shape, but I'm iffy on that description.

Better view of that red horse (Is he chestnut or something else? Not sure!) and his tobiano

It's notated in genetic testing as to (off) and TO (on).  Some people say that if there are dark spots in the white, that means the horse is homozygous tobiano (homozygous = both genes turned on), but that may or may not be true.

This is going to be a theme with the white patterns: they can hide. There's a theory - or at least there was - that there are either white enhancers or white suppressors (or both) that determine how much white a horse expresses when it has basically any pattern but the Appaloosa ones (which have their own rules on how they express white).  That means that how a given gene can show can vary wildly from horse to horse.

Tobiano can range from high white socks (usually with even, smooth edges) and a white tail, all the way up to just the head being dark and everything else white.  You can get dark horses who just have a single white spot that crosses their spine.  Googling "tobiano horse" shows a lot of cool examples, although quite a few of them are mixed with other patterns!

Minimal expression of tobiano at the local show

Frame is the nasty one, in my opinion.  Remember, it's got that alternative name of lethal white overo, and it has it for a reason.

Frame is a dominant gene, usually notated as o (off) and O (on), but the chance that you'll ever meet one with both copies turned on is very, very low.  All of these color and pattern genes are mutations of genes the horse as a species already had.  Most of them are pretty benign mutations - they don't really affect anything negatively.

Frame is different.  Frame actually affects the development of the colon when you've got two copies of the gene turned on.  And by 'affects' - it stops it. Foals who are OO are carried to term normally and are born white or near-white.  They typically have blue eyes.  And within a few hours of birth, they start to colic, because their intestines don't actually work, and they have to be put down.

And frame hides pretty effectively sometimes.

In its largest expression, you get a horse where - well, think of it like you're looking at a drawing of a horse.  All the edges are colored in, and the middle is white.

You know, kind of like this. (From a local show)

Or this guy.  (From a local show)

The pattern is generally termed horizontal - it goes along the length of the body, not up and down - and it only ever crosses the mid-line of the body if another pattern is involved.  The edges are jagged and uneven.  Tails stay dark, but the face may have bold white.  Frame can also cause blue eyes.

In lesser expressions, though... it puts points on socks, and that might be all you can see - or it might even just turn the horse's eyes blue, if the horse doesn't have white.  It likes to make other patterns jagged and sharp around the edges, and if the other pattern is big enough - like, say, a large tobiano pattern - those sharp edges might just be all you see of it.

What this comes down to is: test your horse if you're going to breed, if there's any chance mare and stallion might have pintos in their pedigrees and you don't know for a fact that their parents don't have frame.  Don't be the backyard breeder that doesn't test and then goes on FB or forums begging for sympathy for your sick foal.  Don't be the breeder that gets a white foal and puts it down because you assumed it's a double-frame because it's white; double creams can look white and other patterns can produce white foals with perfectly healthy intestines.  Just... don't.  The test is like $25 in the US plus postage to mail in some hair; if you're breeding horses with pinto patterns, you have no excuse.

*cough*  Sorry, had an opinion caught in my throat there.  Let's move on.

Splash (or splashed white) is kind of fun.  There are actually four documented versions of splash - SW1, SW2, SW3, SW4, and a theoretical SW5 (or more).  And off is just sw.  Like cream, it seems to be incompletely dominant; one copy turned on gives you white, and two copies turned on gives you more white.

Two copies gets complex, though, when you've got this many possible types.  Homozygous SW1 (two copies turned on) is fine, and not uncommon.  So far, they haven't found horses with two copies of SW2, SW3, or SW4, so the theory is that those foals may just be aborted in utero.  However, there are horses with test results showing two different versions of splash - say, SW1SW2 - and those are obviously walking around just fine.  (No SW2SW3 documented so far, though.)

As a general concept, highly expressed splash white looks like what would happen if you picked up a model horse and dipped it toes-first into a bucket of white paint.  The topline stays dark, but the face, body, and legs are white, and the tail may be too.  Lesser expressions aren't quite so dramatic.  High white socks/stockings and white belly spots are common.  So are bottom-heavy blazes - where the white on the nose is wider than the white on the forehead - and bald faces.  The edges of the pattern are crisp and even, and blue eyes (or partial blue eyes) are common.

Possible splash - look at that white face!

One side note - if the white reaches the ears, which can happen, there's a chance that the horse will be partially or completely deaf.  It's not true for all horses where the white reaches the ears, because it apparently depends on whether the white reaches the inner ear, but it does happen.

Splashed white 1 is far and away the most common of the four.  It's been found in everything from stock horses to Icelandics to Shetlands, and it's theorized to date back to before the development of most modern breeds.

Borrowing from Wikipedia again - pretty high white expression here.

Splashed white 2 traces from a single QH mare foaled in 1987, apparently, and there are rumors that it's related to the Gunner line of Paints as well.  It looks pretty similar to SW1.

Splashed white 3 is similarly a look-alike for SW1 and thought to be related to a small group of horses; at the time the paper that identified it came out, there were only two examples known.

Splashed white 4 is even more rare!  It showed up in a single (and sterile) Franches-Montagne horse and is sometimes called macchiato.  Equine Tapestry has a great post about him here.

Splashed white 5 and up are mostly theoretical at this point, as far as I can tell - they're believed to exist, but there don't seem to be tests or completed studies yet.  There's some talk about an "Appaloosa splash," but the paper it points to doesn't seem to talk about that at all (as best as I can tell).  There's also a family of Australian stock horses - the Bald Eagle line - that look splash, but thus far haven't actually tested as splash.  (You can see those guys here.)  There are also splash-like (and sabino-like, which we'll talk about in the next post) patterns in Gypsys and Clydesdales that haven't been identified genetically yet.

The Splashed White Project page at Equine Tapestry is actually an awesome place to see some of the variants of splash - she's got them grouped by gene combinations, so you can look at all SW1SW1 horses, or all SW1 horses with frame.

Some combinations can be pretty flashy!  It's not always easy to tell when you're seeing a combination of patterns, but often the major patterns are easy to spot - up and down shapes from tobiano, jagged white from frame, white faces from splash.

At least tobiano and splash on this guy (at a local show)

Tobiano and frame or sabino (see the ragged edges?), same local show

Other side of the same horse

Tobiano, frame, and maybe splash (looking at his face) at the same local show

Either splash (see the belly spot?) and frame, judging by that neck white and the points on the leg white - or sabino, which we'll talk about next. (At the local show)

Now, let's go back to our theoretical horse from yesterday.  Let's say he has splash.  Now his test results would look something like this:

Ee aa CrC zz DD chch toto oo SW1sw lplp

He gets the toto because he doesn't have tobiano, the oo because he doesn't have frame, and the SW1sw because he's got one copy of splashed white 1.

Next post, I'll talk about the roaning patterns: roan, rabicano, and sabino.