Has an imperial nation been conquered and the forces of the imperial nation then mainly came to their colonies. Even after the home nation gets captured the colonies are ruled and they don't revolt. Then the imperial nation re-conquers the home nation back with help from the immensely helpful colonies and then is able to re-establish itself?
France during WW2
After the fall of France in 1940 the Free France and its Free French Forces were formed to fight against the Axis powers. From colonial outposts in Africa, India, and the Pacific, Free France steadily took over more and more Vichy possessions.
After Operation Torch (the Allied landings in North Africa) Free France retook much of his north-African possession and the French Army of Africa switched allegiance to Free France. This caused the Axis to occupy Vichy in reaction.
The forces of Free France fought their way back into France, first by participating in the Allied invasion of Italy and then in the Normandy landings.
The Wikipedia page of Free France has a lot of information, with a detailed maps of the colonies participating.