A buckskin foal is a foal born with a golden coat color (can be different shades of gold/beige) and will eventually develop a black mane and tails. The black mane and tail may not be present at birth though, the black points usually darken with age.
Will a Buckskin Foal Change Color as It Ages?
Short answer - Yes! Buckskin foals are often mislabeled as palomino or bay, as they are usually born not looking like a buckskin. The foal coat color will almost always change as the foal ages, and many buckskin horses never stop changing shades throughout their whole life. Some sooty buckskins can be born dark bay to the eye, but change color as they mature. Silver buckskins, on the other hand, may be born with a palomino coat color and develop the black markings later on.

Photo: FB Nicole Guetler (buckskin mare and buckskin roan foal)
The Swedish warmblood Buckskin foal Zapphire, for example, was born looking like a palomino with four white socks. However, as he got older, the black in the mane, tail, and legs became more distinctive. He is now a buttermilk buckskin with white frosting in the mane and tail (a very unusual coloring for a warmblood buckskin horse). He looked like a palomino at birth but slowly darkened into a buttermilk buckskin color.

Photo: Famous Colt Zapphire Boy
Even though the lower legs have white markings, they are still regarded as buckskin coat colors as the legs are black underneath. The white in the mane is called frosting and usually darkens with age.
Is Buckskin the Same as Dun?
No, this is a common misconception. Even though dun horses also feature the distinctive golden body color, they also feature a dorsal stripe over the back and may have other primitive markings such as shoulder and leg stripes. However, because they feature the same base color as Buckskins, they are often mixed up to the untrained eye.
Photo: FB Amanda Lawrence (Smoky black buckskin foal)
How do you determine whether your foal is a Buckskin?
If one of the parents hold copies of the cream gene, then there is a chance your horse is a buckskin. To be 100% sure we recommend a color genetics test. If you are based in North America it can be done with Etalon.