Tips on recoloring a monti cap

[GHOSTLY]

Just got back from a family friends house who had a monti cap which sat upside down in the sandbed for a while. The piece was originally a bright green and ofc due to the piece being upside down its lost a lot of color. Any of yall got tips on how to bring that bright color back?
Piece still has polyp extension but super weak

Their tank:
Nitrate 50
Alk 11.7
Calcium 380
Mag 1270

Mine
Nitrate 5-10
Alk 8.3 (bringing this up to 9 slowly)
Calcium 420
Mag around 1370 last checked 2 weeks ago at an lfs

 

[Kooma]

I’d just let it be in a medium flow and not too bright spot for a week.