Sexing the yellow opaline turquoisine -beak colour

I've got a new yellow opaline turk hen (2010). She's very similar to my other yellow opaline turk that I got a month or so back, apart from she has a much lighter beak. This lead me to believe that the darker beak bird may be a cock.  This seamed to fit as pictures generally show yellow opaline cocks with darker beaks than hens. Also the hen I lost this year had a lighter beak than the cock.

Latest new hen (light beak)

Previous new hen. Is this a cock? (dark beak, some red on head and darker blue)

My opaline yellow cock (dark beak) and opaline yellow hen that died this year (light beak)

I thought I was on to something with the beak colour, however I've just got the DNA results for the new dark coloured beak bird and it is a hen.  I suppose its beak is not as dark as those of the known yellow and yellow opaline cocks, so there may still be something in it.

One thing is for sure the yellow 'hen' I also got this year is definitely a cock (also dark beak)....

And the cinnamon that I bred this year is a cock (dark beak)....

So I'm going into the winter with 4 cocks and 3 hens. I had intended to have more hens than cocks.  The other cock, is my reliable red fronted normal (dark beak)....

and my cinnamon yellow hen (oh, it also has a darkish beak)...

Opaline yellow cock and young cinnamon cock (dad and mum above)