The reds are small and have almost no membranes or seeds, several totally clean inside. I am only saving the seeds from the red ones. I have had no luck getting younger seeds to germinate, even with a heating pad and 3 weeks. 
BTW prepackaged Shishito’s in the grocery store again. 8 oz bag 3.99. Last year was the first year I saw them, many bad, should have been tossed.
Take some of those blackberries & make a batch of this - a favorite among my family & friends. I use the cheap Oak Leaf Merlot from Walmart - the merlot flavor really comes through in a nice way:
Blackberry Merlot Jelly
https://highlandsranchfoodie.com/blackberry-merlot-jelly-recipe-holiday-gifts-from-the-kitchen/
I use the 2nd method in the post:
Sure-jell low sugar pectin and followed their directions on the insert for the process.
The 2nd batch jelled within a couple hours. Sure-jell has you mix 1/4 cup sugar with a packet of their powdered pectin. You bring that mixture and the wine and berries to a boil and then add the rest of the sugar. Bring to a boil for one full minute then pour into jars and water bath.
My note: when you dump the rest of the sugar in, don’t panic!! Just keep breaking up the clumps - you have enough time to get them out before the mixture boils.
They’re so pretty when they go to red! :)