Like Queen Ingrid, Queen Friedrike also wore feathers to her son's wedding.  Again -- so sixties, so perfect for a queen.  You can see the powder blue color of the hat better in the family photo:

Friedrike's standing immediately to her son's left.

Lots of bling in this picture, but focus your attention on the left-hand side, and let's talk about the tiara worn by the mother of the groom, Queen Friedrike, shall we? 

This diamond tiara -- Queen Sophia's Diamond Tiara -- was brought to Greece by Friedrike's mother-in-law, who was born Princess Sophie of Prussia.  When Sophie married the future King Constantine I of Greece in 1889, she was given this tiara by her mother, Empress Frederick of Prussia (who is probably more familiar to royal history buffs as Princess Vicky -- the eldest child of Queen Victoria and Prince Albert).

The tiara was a truly impressive diamond sparkler, and one that I wish we could see either Queen Sofia or Queen Anne-Marie wear today, but alas: most believe that, strapped for cash, Friedrike sold it at auction in the '70s.  However, some royal watchers are still crossing their fingers that it's still in the family and will make a brilliant reappearance sometime in the future -- like on the head of royal bride Tatiana!

Tough to see the details of the hat that Queen Fred of Greece wore to this wedding; besides this black-and-white snapshot, we get only a little glimpse of it here:

She's the one to the left of Queen Ingrid (in the second row, wearing green) -- looks to me like we've got pale blue feathers here, perhaps?