They are either traffic flow camera's or ANPR.. Only gray ones i see are forward flashing for gatso's and the type above but with red lights in them (like what you have on cctv sometimes), red light and bus lane camera's..
Plus if they are under test I don't think anything can be done (don't quote me on that,lol)..
I remember reading that yellow are local government and gray are govourment at one point but 99% of all new cameras are yellow...