When you look at this photograph the headlight is selectively blackened relative to any other part of the upper cab. You can see from multiple photos the patterning of soot and dirt on the lamp but just as there are black and silver 071s with orange doors, and IR logos on Supertrain livery, one other possibility might be that the headlight has been replaced by a spare, in black, from the preceding livery.
Lovely shots!! Green has not been my favorite livery in the past but it is growing on me:-bd