Red are left on the vine to ripen further. Slightly sweeter than green, kind of like a Green bell pepper vs Red.
I picked up 2 pounds of Fresno peppers at lunch... We'll see in about 7 days how different the final product is ...
FWIW... Fresno's were $4.99/lb today and the Red Jalapenos were only $1.69/lb from the market across town... Even if the Fresno's work out, it'll be about $10 for the bottle. Back when Huy Fong was plentiful, a bottle was only about $4-$5 around here...