Okay, for me, first I want to say,
I have never grown a Serrano pepper
so, I can not say from first hand experience..
I have grown Cayenne's, Jalapeno's, Hugarian Wax peppers
, Bell's, Sweet Banana, and Chili Habanero's.. *those last one's didn't do so great, but I got a late start*
So, like I said, I have no experience in actually growing
I basically went on idenification by looks...
The one's in the picture posted, had a point to the end..
And any reading I did on the Serrano, all had blunt/round ends.. and the body's of the pepper
's look meaty...
The one's pictured in the post, to me, gave me more of a Cayenne *type or style* look, long, thin, *sorta* and pointy and non~meat *thick walls) inside..
But Jimmy very well could be right, if he's grown them, and he would know what variety he picked and grew better than I would...
Did we ask you yet GD if you've tasted them yet???
And to your question, about when do they turn red..
In my growings', mine turned red if I left them long time on the vine *turned in succession of a peach/orange then to red* ...