Should I use green or white tape ?
The color of fencing that you choose does not alter the performance of the fence, you may choose green over white fencing if your able to view it from your house or other people can see it as green obviously blends into the background more effectively, research suggests that horses can see more effectively in the blue ,green part of the color spectrum. Horses generally become very aware of their boundaries quite quickly. The purpose of electric fencing is that they are respectful of the electric shock that they get form the fence rather than the physical fence its self.
Compare the two views .... The two picture where taken from the same point in the field
Field with standard White 20mm tape :