I'm glad to hear he's healing up!
I wonder if the purple is some type of discoloration since it's been there so long. I don't know though.
We can ask @Eggcessive if she may know why the purple/color is like that, it's been there for a few months right?
I'd continue with the daily debridement since that what seemed to work best.
I'm not seeing the ingrown feather, can you circle it?
Generally, for an feather under the skin, you'll want to swab the area with an antiseptic (Chlorhexidine would be good), then use a sterile needle and begin to...