The majority are operated by TFL under orange lights but a few are used by BTP/TFL under blue lights, all the lights can be swapped out for either blue or orange and the battenburg on the BTP ones goes over the TFL livery and can be removed.
https://farm5.static.flickr.co…44827058_41bc61a872_b.jpg
https://c1.staticflickr.com/4/…72310501_cdd8a71f50_b.jpg
There is a video showing this somewhere but i cant find it
Thank you for sharing your knowledge on that Tacr