How to sex coturnix quail

[Hilltop farms]

I have about 20 odd quail that are about 4 weeks old and was wondering how I should go about sexing them?
I have the following colors:Tibetan Italian Japanese Texas A and M and a few tuxedos

 

[paneubert]

Read the first post at this link.

https://www.backyardchickens.com/t/102281/coturnix-quail-basics-information-and-pictures-galore