Hairspring Steel Type on Vintage Omega 620

I'm working on a vintage Omega 620 for my wife which had a bad hairspring along with needing a new mainspring and a lower balance shock (incabloc) setting. I purchased a donor movement that had a good balance, and the setting I needed...the mainspring I just purchased.

The steel of the hairspring is the blue carbon steel and not the white steel that I've seen in every watch I took apart in my short time tinkering with watches. When did Omega stop using the blue carbon steel springs? I don't want to put in a hairspring if its not the proper type steel. The movement it came out of is from 1968.

Thanks