Answer:
Although You may think they are brown, you're wrong. The Nevada bighorn sheep doesn't have to be brown. If you take a look at the google images of the Nevada bighorn sheep you will find it can be a light black, light brown, dark brown, or even grey and white. Just because you have seen one picture of the Nevada bighorn sheep and it was brown they are all brown. So take a look at all the pictures.
Sabrina Carroll's answer!