Seeking Recommendations for Organic Diastatic malted barley flour

barley flour?  

only if the malted barley flour is diastatic.   If not labeled diastatic, then it probably is not.  (I think barley powder would be flour unless it can be concentrated to a crystiline form.  Look at it under a mycroscope and see if it isn't just flour.) 

Are there color differences that would indicate the obvious? (Toasted barley flour would not be diastatic because if heated high enough to brown the diastase enzymes would no longer be active.) 

Diastatic malt and non-diastatic malt are very different (although both will both provide some coloring). In tiny amounts, diastatic malt will greatly change the enzymatic rate of starch breakdown in the flour, and hence change its fermentation properties. "How much" is a big question; the "right" amount is highly variable depending on which wheat was harvested when and what the weather had been. That's why millers in north america typcally list diastatic malt (they sometimes call it "barley flour") as an ingredient in their flour, but you can't find out exactly how much they use no matter what  ...it varies with different batches!

As far as I know, the minimal way to figure out "how much" is to get the right equipment and procedure to measure the "falling number", mill and mix a bit, test the "falling number", and adjust the amount of diastatic malt until the "falling number" is within your desired range. Doing it at home for a whole batch of flour all at once is risky, as either a slight error in the amount of diastatic malt or a less-than-thorough mixing can ruin the whole batch. For whole wheat flours, I'd suggest the safest thing is to leave the diastatic malt out of the flour altogether, then add tiny bits to individual recipes as needed (if at all).

I'm curious: what instructions told you to put diastatic malt in home-ground whole wheat flour anyway?