Insulators and Earth at Sandwell Valley

 We were at Forge Mill Farm in Birmingham and I noticed that the insulators on these seemingly identical pylons had different colours. I can't find any reason. 11 insulators might be 132 kV wire (see http://www.epemag.net/electricity-generation-pylons.html which says 9 are needed) As I had binoculars with me I inspected the thin wire that comes down the left hand side of the pylon. I'm assuming it is an earth wire. I read https://electronics.stackexchange.com/questions/73726/what-is-the-purpose-of-the-thin-wire-at-the-top-of-power-transmission-lines. I'm wondering if it is actually because the guard wire along the top is used for communication in this case. This needs more work but I started at https://en.wikipedia.org/wiki/Optical_ground_wire