It's a beautiful scene with a majestic horse standing in a lush field of green grass. The horse is a mix of brown and white, with a thick mane and tail flowing behind it gracefully. To bring out the horse's muscular form, try using darker and warmer shades of brown for its body and hooves, while going lighter and cooler to define its mane. To create a nice contrast between the horse and the grass, use a bright and sunny yellow for the grass, with popping hints of green and blue scattered throughout. Don't forget to add some wild flowers in the background to finish off the picture.