The Realistic Horse Genetics mod (1.18.2, 1.16.5) adds genetics that are biologically correct for Minecraft horses. Horses can come in many colors, including dun, palomino and bay, black, buckskin or chestnut, gray, pinto, leopard-spotted, and others. This is not a difficult topic to understand. You can breed any color you want and you will likely get more. Recessive genes may give you an unexpected color. These color genes include: extension, agouti and dun, cream, pearl, gray and silver dapple. These genes can be tested in real life, and they can also be tested in games using a book on horses. Hidden genes are also possible, but they are not easily tested. These hidden genes control traits that aren’t known in real-life. Hidden genes can affect flaxen, seal, sooty and rabicano as well as shade variation and how fast or slow a gray horse’s color changes.
It is often easier to find a horse than to breed it in vanilla Minecraft. Breeding is a good idea because genes control the stats. Horses will spawn with average stats. Foals can be just as likely as their parents to be more successful than their foals. This is a significant difference to the vanilla system where foals almost always outperform their parents. It is much easier to breed horses with good genes once you have horses than it is with the vanilla system. You need to be cautious, however, as there are certain pairs of horses that will always produce foals who are just as good or better than them. Horses that are too closely bred can cause this. Inbreeding can be avoided by having more horses or, if you have too many horses, by breeding them to a different horse.
Horses come in a variety of sizes. The majority of spawn will measure between 12-15 hands in height, but it is possible to breed miniature horses or draft horses. Sometimes, smaller horses can be accommodated in smaller areas (sometimes even on boats). Larger horses are healthier and can be ridden by heavier riders, while smaller horses are more comfortable. Tip: Avoid inbreeding small or large horses and ensure that there is high genetic variation. Even horses that are not the largest or smallest in size may still have some of your desired genes.