I sounds like you pushed out some old bile that was stagnated in your liver from the stones.
The older the stone the darker the color. I would summise that the darker stone cover with a lighter color was that it was being encased by newer cholesterol wax.
Did you have a burning sensation during some of your movements? That is when real toxic old bile is being passed. Sometimes it is so intense I take a partial bath afterward. I also make my own wipes with aloe juice and water. It helps to coat your rectal area with vaseline as others suggest, or shea butter is a more natural alternative.
Make sure your bowels are moving well and take psyllium or other bulking/absortive agents to get those toxins out of your bowels.
Of course a colonic or enema would be beneficial too if you have access to the treatment.
Keep well hydrated and plan to flush again in the next couple of weeks. You are doing great!!!!!!