I have a ten month old cock who has been through two moults and he still has not got his mature blue cere. All his sibling have, he is the youngest but there is only 6 days between him and the oldest. His sibling are all female. Do female's mature quicker?

It varies from bird to bird Merlin had a blue cere during his first molt.

First moult is usually around 3 months old.

 

Recessive pieds, Dark eyed Clears and Albino cocks never get a blue cere.

He's had his first moult and he's not a peid, dark eyed or ino. He's a normal green cock.

Are you sure 'he' is not a 'she'? In a normal green, the cere should be very blue by almost a year of age, I think when much younger you would be able to tell. What color(s) are the cere in this bird?

It is purple

Is the purple tone concentrated more towards the top of the cere and is bluer towards the beak?

 

The cere is blue and a nice cock bird at that.....

Sorry the photo's were bad I took them at night and my bedroom distorts photo's.

So is he just a lighter blue because he's young?

The blue looks normal on my monitor, Jodie.