John.
That was an older post of the green dilutes that some were showing more blues on the head than others.
Here is another post of a blue pastel (blue back) that Tiffany bought.
http://finchforum.com/viewtopic.php?f=7 ... +with+blue
We both had an interest in this unusual amount of blue on the head. All black headed dilutes have a the blue ring around the neck in different thicknesses and brightness. Some actually have the blue on the top of the head and cheeks.
Here is a young bird in earlier post at full maturity...lots of blue
I took pictures in different lighting because many times the camera will give the illusion of blue due to the reflective qualities of the light grey heads, especially if using a flash. All the below pics are without flash and are inside lighting, outside sunshine and outside shade. I also put him nest to the purple passion flower to show the blue head and breast color compared to the true purple flower.
Aslo here is a site from a beautiful dilute that was produced outside the US
http://users.skynet.be/fa398872/engoulm72.htm
Unfortunately I lost my male a few months ago.

But I have 2 chicks from him, 3 sisters and have bred his parents again and looks like they have produced 3 more like him

though they are only 8 months so It will be another 6 months or so before I know how much blue they will get.
In the picture yours looks to have a good bit of blue overcast, to the cheeks also. Do you know how old he is? Maybe we could swap bloodlines someday if he does have the blue and if you are interested in trying to establish this blue headed gouldian.
Sorry for elaborating so in your post. But thought I would try and explain the blue head statement.