I have observed that some areas have some power transmission towers painted in Red and white colors. But, more often, transmission towers are unpainted. An illustration of what I mean by this, enter image description here
Left: red and white tower, right 'regular' tower
If I am right, radio/cell-phone towers are usually painted red and white, but the example in this picture is clearly not a radio tower.
So, what is the significance of a transmission tower being painted in such colors?