Any list out there on the thickness of grape skins by varietal? I've been surprised recently to learn Syrah is a thinner skinned grape than Merlot, Chardonnay is a relatively thin skinned grape, etc. Does it matter where they are grown?
I can't claim to give you the whole story here but I'd be careful of over simplifications between a literal thickness of skin and any one factor. It may be true that thicker skins lead to deeper color in the most general sense, but that of course depends on not just skin thickness but the ratio of skin to pulp, level of anthocyanins, pH, wind effects on grapes, UV exposure, climate, water availability, winemaking techniques, etc etc etc... That's not to say that Pinot isn't more thin skinned than Cabernet. It is. But beyond the most broad generalizations, things get complicated. For example, people often relate the light color of Nebbiolo to thin skin when it is actually quite thick. It's an issue of color pigments, not skin thickness. Just google Tempranillo and thick or thin skin and you will see it's described as thin, medium and thick skinned depending on the source—the latter is probably more accurate despite its sometimes light color. Just a general note of caution: unless you read something with fractional millimeter readings, assume it's as much a figurative "skin thickness" as a literal one.