Thanks for reporting back Agnes! Great idea salting the shiso first. It's also a good way to preserve it for winter (use lots of salt, drain the liquid and store it in the fridge). I'm glad you enjoyed this!

I have tried the recipe with red shiso. I kneaded some salt into the red shiso first, let it sit for half an hour, discarded the liquid and even pressed liquid out of the herbs. I read this suggestion somewhere to get rid of the astringent effect and it worked. I skipped adding more salt and took the liberty to add some pine nuts into the pesto but other than that followed your recipe. The pesto was colored like tapenade from black olives and it tasted perfectly fine like shiso. We added some fried fish, because uni is hard to find here. Our friends with the red shiso plant were happy to find a recipe where they can use a lot of shiso.
Thanks again for the recipe.

Hi Agnes, green shiso has a flavor that's similar to mint and basil (it's in the same family as the two). This makes it really well suited for making pesto. Red shiso has a more floral aroma (even though it's in the same family). It may work (I've never tried it), but the flavor will be quite different from green shiso. As for uses, red shiso contains an anthocyanin that gives it its color which means that it's pH sensitive and will turn vibrant red when exposed to an acid (like vinegar or lemon juice). It's main use in Japan is to pickle along with ume to make umeboshi this is what gives umeboshi it's color, but it's also great to include in western style pickles made with vinegar because it adds a nice color and flavor. The leaves tend to be a little thicker and tougher than green shiso, so it's not great for using raw like you would green shiso, but I've used it in stir-fries and stews before. Hope that helps!

The kind with the purple underside have a sweeter, mellowed flavor compared to the pure green kind

Shiso (known as "beefsteak plant") is considered an invasive alien species here in Maryland, so its range obviously isn't limited to Japan. It just appeared in my garden this year, so now I'm looking forward to eating it.

Thanks!

No difference - just different color.