Royal Navy flag officers did not progress from every blue rank through every white and red rank in separate blocks. The colours originated in a fleet divided into van, centre, and rear squadrons. By Rodney's time they chiefly distinguished seniority within rear-admiral, vice-admiral, and admiral grades. The senior officer of the red squadron was historically Admiral of the Fleet, and Admiral of the Red was added later when the Navy needed another senior post. A colour label no longer fixed an officer to the matching tactical squadron, so a rear admiral of the red could command the van. The system also let the Admiralty reward an exceptional officer by skipping intermediate colour ranks rather than granting only the next incremental promotion.
Notable Point · 1:48:19-1:50:00
How the Royal Navy's colour ranks organized seniority
The red, white, and blue flag ranks grew from battle-squadron organization and later became a fine-grained ladder for promoting admirals by seniority and merit.