Different colors for Power Transmission Towers
In the US, the FAA requires high-visibility markings on any tower that rises at least 200 feet above the "established terrain" (and near airports, the 200 foot requirement may be reduced). The ICAO sets similar requirements, so I'd expect roughly similar requirements in most other countries as well (though it wouldn't be surprising if some details vary).

Power transmission towers are typically around 180 feet tall, so this doesn't usually arise with them--but it can when (for example) the tower is at the top of a hill or ridge that's steep enough that the ridge itself contributes to the rise above the "established terrain". Some towers are also somewhat taller than others, and with the typical height at 180 feet or so, one doesn't have to be drastically taller than others to hit the FAA requirements--the difference in height may be small enough that it's not immediately apparent.

Reference

FAA Advisory Circular 70/7460-1L