Northern is (fairly) uniform now, with only the 321/322/333s in a non-standard scheme afaik...
But up until a few years ago there were 142s in Northern, NS, Arriva, NWT gold star, T&W, GMPTE and Merseytravel. 144s in Northern and the later WYPTE. 150s in Northern, CT/NWM, RR and Gold star. 153s in Northern, Arriva, Gold star and RR. 155s in the revised Metro. 156s in NS, Revised RR (Green stripe), and Northern. 158s in Northern, NS-TPE, 2 different variants of WYPTE, gold star and possibly a few others inherited from other TOCs. For a while Manchester's 323 sets were split between Northern, Gold Star, and GMPTE colours too.
Not sure if all the variations existed concurrently, but up until the last 2-3 years, catching a local train in the North could bring just about anything!