What color would the foal be?
I can't give you an exact answer, unless both the dam and sire have been DNA tested. However, I can give you a rough idea:
If the grey horse has one grey parent, the foal has a 50/50 chance of being grey. If the grey horse has two grey parents, the foal will either have a 50/50 chance of being grey, or a 100% chance of being grey (impossible to know without DNA testing).
Now, if the foal isn't grey, it could potentially be just about any color on the planet without knowing what genes the dam and sire carry.
Kladruber
The answer to this question will depend on exactly how you meant it. If you meant which breed of horse rarely stays black as they age? then many breeds could fit that description, such as the Lipizzaner, they start out bay or black and turn grey as they age, but a few will remain dark. If you meant it as in, which breed of horse will stay black? Then there are several breeds as well, such as the Friesian.
Horses can be most any color except pink and purple or orange. They can be brown, black, yellow, blue roan, red roan, gray, white and there can be crosses between the colors I've just named. There can also be white horses with tiny black spots that are called appaloosa's.
Fresian horse is a breed of horse
yes you can as a matter of fact! you can use your own horse and or a w horse that you have tamed and it depends on what color the 2 horses that you breed are to figure out what the foal will turn out like. like if the father (stallion) is black or brown, and the mother (mare/dam) is white or grey, then the foal might turn out to be white at the top and black at the hooves or grey at the top and black or white at the hooves... or it can be mixed!
Kladruber
A Black horse
If you breed a black horse and a gray horse, you can get quite a variety of colors. If the gray horse has a black base (was born black), then the offspring will either be black or black-based gray. If the gray horse is chestnut-based or bay-based, however, you can get black, chestnut, bay, black-based gray, chestnut-based gray, or bay-based gray. It's most likely that the gray horse is black-based, though genetic testing would probably be required to find out for sure.
A black horse
It varies with the horse, but generally you will get a dark grey colt or filly. This is because the genes of the darker horse will make your foal a darker colour but the lighter of the pair kepps the colour from becoming completely black. Example: Cremello Stallion x Chestnut Mare = Either buckskin or palomino.
all horses are black
Kladruber
Is the horse really white or is it a gray that has faded with age. Gray horses start out life black, bay, even chestnut, but all fade into grays. Several breeds come to mind and one of them is the Percheron. Gray is the most common color for this breed. Another is the Shire. This breed comes in a wide variety of colors, gray being one of them. Any of the draft breeds that have gray in their bloodlines could look white. The Lippizan is another breed that is predominantly gray but they are smaller in build and height. There other possiblilties but these would probably be the most common.
Yes, Thoroughbreds are the fastest horse breed in the world. Also the colour of the horse does not affect the speed.
Kladruber
Frisians are all black horses.
They go by type not breed. if the horse is of the right type they will use it no matter the breed.