I can't see the photos at work (most are blocked) so what color are they? What patterns?
A horse can be homozygous for just about any colors.
A black horse can be homozygous black (EE) or heterozygous (Ee). If the former, he can ONLY produced black BASED horses. If the latter, he can also sire red BASED horses.
Chestnut is always homozygous for the recessive, ee. Chestnut to chestnut can ONLY produce chestnut.
Bay is caused by agouti acting on black. A horse homozygous for agouti (AA), regardless of being black or red based, can never produce a black horse, as any blacks would end up being bays. Chestnut is not effected by agouti, but they certainly can have it... I have a chestnut mare who is homozygous for agouti (tested) so she can never have a black baby.
Then some other genes that act upon those:
Cream. Crcr, one copy, makes chestnuts into palominos, bays into buckskins, and blacks into smokey blacks (which almost always look just black). Two copies (CrCr) turns chestnuts into cremellos, bays into perlinos, and blacks into smokey creams. Those three can be hard to tell which is which without testing.
Silver is Z. ZZ and Zn dont' look different. It only acts on black, so a chestnut wtih silver looks like a chestnut without.
Champagne is CH. I don't know all the different champagne terms, sorry ;) But it does act on all colors.
I'm not too good with pearl, either... but one copy doesn't make a difference. But if there are two copies, or one with a cream gene, the color changes.
Dun is Dn. Can be hetero or homozygous. On bay: dun, aka zebra dun. On chestnut: red dun. On black: grullo. A horse can be buckskin AND dun, and sometimes is called dunskin. Or palo and dun: dunalino. ect.
Grey can affect ANY color. One copy is Gg, two is GG. If a horse gets G, it will grey out, period. Often, the lighter colors will darken as they start to turn grey.
There are four pinto genes. Tobiano, frame, sabino, and splash. Frame can NOT be homozygous... those horses die within a day or so of birth. THe others can come in homozygous. There is a test for tobi and frame, and ONE version of sabino: there are SEVERAL different sabino genes!
Appaloosas have more than one gene, too. The main gene is the leopard complex (which does NOT mean a leopard horse) which is Lp. One copy and the horse is an appy. Two and it's homozygous appy. If a horse has only Lp, not the other appy genes, it will be a varnish aka appy roan. Mottling, sclera, striped hooves, and will, over time, get roaning.
The other genes are the PATN genes. This is what creates blankets and leopards. If a horse gets a PATN but NOT Lp, it will be a solid colored horse. If it gets ONE Lp and PATN, it will have spots (spotted blanket, leopard, ect). If a horse gets TWO Lps and PATN, it will be a few spot, snow cap, or few cap.
This si why it's trickier to breed for appies: it takes TWO genes!
That's horse color in a nutshell... and it's very possible I've left something out on accident ;)
PS you can test for most colors. I use this lab: Horse Testing - Equine Genetic Testing
most tests are $25.
PS I have a mare is is Ee Aa Crn Zn Dn+ she is a silver buckskin dun, and can produce just about any color! :) (she had a chestnut foal this year (her first foal) haha!)