Green poo can be a sign of oversuppy. Which would make sense if you have increased your supply. Cluster feeding in the evenings is actually very normal BTW. Are you still expressing?

Also, with the forceful letdown, posture feeding can help (feeding lying on your back with baby across your chest), or leaning back while feeding (make the milk work against gravity).

If your baby isn't showing signs of distress from wind etc, then I wouldn't be too worried about the colour though. In itself it's not a problem.