Cheers to Dustin Chabert, Jeremy Eubanks, and Rachael Ryan for last week's responses on Extended Maceration!
This week: Red Wine Color in Tasting
From a blind tasting perspective, discuss the various elements that can impact color in red wines.
A few other points to tack on to Dustin's excellent response:
Color fixation in a red wine is mediated by a couple of different factors: first off, the quantity in the skins of the grape (i.e. malbec, tannat, p. verdot, etc.), but in order for that color to make its way into the finished wine it has to be 'fixed' or stabilized. Tannin binds anthocyanins, so the amount of tannin in a red wine can also impact its color - the chemical mechanism of viognier/syrah cofermentation color stabilization in the northern rhone (i.e. viognier is a highly phenolic, read: tannic, white grape - it provides the extra phenolic oomph to bind the anthocyanins of syrah). However, that reaction is also significantly impacted by must acidity, with the anthocyanin binding reaction hindered by high-pH (i.e. non-acid) musts.
TLDR: high-acid wines, even from highly tannic grapes (like Sangiovese and Nebbiolo) tend more towards the red side of the spectrum than the blue, because the low must pH prevents as much of the color from the grape skins stabilizing into the finished wine, and that color instead precipitates out as sediment at the bottom of the tank or barrel. How does this tie back to blind tasting? As much as everything is on a spectrum, coupled with an accurate assessment of skin thickness and maceration from the staining of the wine, one can begin to form ideas about acid as well. These three elements (skin thickness, acidity, alcohol) collectively are a wealth of information towards the identity of the wine, even before the first whiff is had (re: Master Beteta's exercises). If anyone wants more detail on this whole rat king of chemistry, Clark Smith's chapter "The Vicinal Diphenol Cascade" in his book Postmodern Winemaking is a great (if not necessarily thrilling) read.
The only other area to expand on I think is assessing not only the scope of rim variation (i.e. purple core to pink rim, or red core to orange rim), but also the intensity or width of that rim variation - is it a gradual even fade or a pronounced, sharp drop off? I have found that wines that see extended barrel aging, usually on the order of 24 months plus in small barrels, tend to have a very narrow band of pronounced rim variation - which I most classically see in wines like Rioja, Brunello di Montalcino, and Bordeaux.