I dyed my hair bright blue early in the pandemic, so had the blue-black dye at the ready to be workplace appropriate. It was something I dreamed of doing but never was the right time because I had to look professional. I kinda hid from video calls for a bit, but my manager saw my hair she mentioned that our employee dresscode does not include anything on hair color. If I was interviewing, I'd likely go with that blue-black like your candidate did, but I have two decades of conditioning that unnatural hair colors aren't professional.