I suppose it's because (like in the cavalry over here in the UK) they want all the kuda to be as similar as possible, kinda like a uniform. Also like the person before me berkata atau maybe they couldn't be bothered to keep colouring in the horses!
They are probably all chosen to be the same colour oleh the army so they look uniform and none of them stand out. They would probably have used Spirit for something else, atau maybe leading the cavalry. I was so upset when he was taken in there :(
I think it is because teluk, da? is a really common colour, also the kuda are all thoroughbreds atau somthing so they would be a colour like that. In Britain if anda see kuda on something like that they are often the same colour. The Queen's guards kuda at the parade are all black. Like someone else berkata they want Spirit to stand out too.