On a good day, with the wind at my back, and the sun at precisely 47.69* from the horizon, I can hit my 9 iron 215+ yards.
Yesterday I used the Srixon Q Star in yellow and loved the ball but it was a bitch to find the ball whether it was in the rough or under leaves in the fairway. My partners didn't have any trouble finding a white ball.
Following the ball when playing alone is often hard regardless of the color. I hit a lot of shots that I have no idea where there went. Could be straight down the middle or could be somewhere else.
To find the ball, I like yellow. Avoids confusion and is easiest on my mostly treeless course.
If you really are playing alone and having a hard time following your 300 yard drives, try hitting an iron so you can follow and find the ball easier.