P8ntCrazy that is mostly right except Bay or Zebra duns aren't always lighter. I have a bay dun filly and she is a dark bay. She has some leg barring and spidering on her forhead as well as ear tips and a dorsal strip. She comes from a long line of duns that gray out. She is staying dun. So not all bay duns go lighter. They almost have the test at UC Davis for the dun and then I will have her tested.