Sexing my redbreasted button quail

[isegal]

I have 5 button quail that are 31 days old. I have two whites, two redbreasted, and one silver. I've noticed one of the redbreasted is significantly smaller than the other, and also has some red on his tail area, so I think he's a male, but possibly not since the whole point of redbreasted is to be red? The other redbreasted is bigger with no red and slightly paler colors. I've noticed that the one with the red tail acts different than the rest, like a male. He's the smallest and the most skittish. Often when I approach he jumps away or even into the wall! I haven't seen any of the others act like this. Also, I heard that the males will make a sound sounding like "PEW Pew pew" going down in level. I've heard this call many times, but never two different ones at the same time, so are the chances that that one is the only male? LMK!

Images showing the two redbreasted.
One of the bigger one, two of the smaller.

 

[Nabiki]

You need to look at the feathers around the vent. If there are red/rust feathers around the vent, then it's male.

Males are usually smaller than females (but there are exceptions). Males are usually less skittish than females, however, so I'm not sure what you're characterizing as male behaviour. Does it growl? Make a whistling call? Does it offer treats to other birds? Those are typical male behaviours.