I agree, very nice setup.
Your two Blues are showing a lot of barring on their backs, plus a lot of shiny colors in both green and blue(blue is important for recognizing a male) on their necks. Girls same age as these two already look like mini-peahens, with a much more solid and dark body with less shiny feathers on neck and only in green.
Compare the patterning on the blue males to the patterning on that cameo girl.. notice she has a very solid and even colored back. That's the female blue pattern(except she is cameo so the color is not same, the only difference). A male cameo would show exactly the same patterning as on your two blues, except in shades of lighter and darker tans.
The very first pic is excellent for comparing the male patterning(the two blues) with a female(the one cameo) patterning.
Ditto for the pieds, on the colored areas.
Your black shoulder is a male because of the amount of dark color on his back and also the shape of the dark colors. Female black shoulders at his age again, already look like adult black shoulder hens.. less color and the dark colors are shaped differently.