Class 86 only wore Electric Blue for a short while, as their building coincided with the standard loco livery changing to Rail Blue (darker). If I recall correctly the later ones were built in this livery.
At those times it was not common to drag the locos on diversions, they were generally removed and a diesel substituted instead, not that there were many instances in those early days of electrification once it had been commissioned. Also on the West Coast line Class 40 were common but Class 37 not so.
What was more common, which later mostly disappeared, was to have two electric locos at the head of the train, the second one dead with pantograph lowered, because while the electrification was in progress the loco diagrams were notably unbalanced, and this was used to move them round for their next service.
