What colors to make buckskin?

^^ Gorgeous mare and foal BTW!

Look up zillionaire he produce buckskin or pallys to a chestnut mare. His sf without a guarentee was $1500 I think . 2500 guarenteed. And look at http://www.blazingcoloursfarm.com/ her studs , I think more than one also produces what you are looking for.

How can the owners decide to guarantee color or not??

They do gene testing. Most stallions with these passing on's are guarenteed proven color producers.

Sometimes it nothing more then an advertising ploy. I did it for a few years to get certain mares into my stallion. Even though it was all up to the mares for those colors. It is just a way to get some good mares in. I had several restrictions on the deal not just more money.