The breed is not important, the genetic pattern is... so for instance you could use a brown leghorn, but you could not use a white leghorn.
If I’m not mistaken the link I provided states that it is the chipmunk down patten of the chick that is the key... but it’s been a long time since I’ve...
Here’s a “recipe” for doing this... the breeds are not important, but you need a ‘wild type’ patterned and a barred patterned bird as described
Edit to add:
So to try to get your speckled green-blue autosexing you could try by using a welsummer instead of a brown leghorn and cream legbar...