Thank you Beth. The tiara/brooches originally being turquoise makes much more sense. If you had a turquoise tiara you would alter to either pearl or diamond which is more useful and goes with more things.

It is odd that the jubilee was altered to match as well as the tiara. It would have been a more simple job to alter Just the tiara and they appear to have been altered quite close together. Turquoise is not a practicable colour.