I can't venture a guess why it looks greener but with a CYA of 55, Ben's Best Buess Chart shows that you need to raise your FC to 15-20 and keep it there to fight the algae. Trouble is, if you don't hit it hard enough you're wasting your time (and chlorine). More Bleach!

The plan for fighting algae is:
Raise FC to shock (per Best Guess Chart) and keep it there.
Test FC and correct as often as you can.
Run pump / filter 24x7 and clean filter as necessary.
When you hold FC overnight and have less than .5 ppm CC, you have won, let the FC drift back down.
Apply POPP (Pool Owner Patience and Persistence) liberally.

PS Waterbear and I were posting at the same time. He may be onto something regarding metals and you do need to be specific about the readings being FC CC or TC. But I think he and I agree you likely have an algae bloom and that's what this plan aims to fix.