I think most breeds tend to sell well for wild horses. I personally stick to catching only 4 & 5 star horses. 

As for colours and patterns, plain horses will probably sell for a little less than patterned horses, especially if the pattern is a variation. Dapples can also be highly sought after. Greying horses tend to be the least popular and you may find it harder to sell horses with the grey gene.

I’d suggest always checking the genetics on any wild horses you catch (done at the vet). It’s relatively low cost, but will let you see if your horse carries genes that can be harder to come by and that aren’t visible e.g. thoroughbreds or Arabians that carry manchado, shetlands carrying mushroom or horses that carry flaxen. These horses will likely sell for more.