This page exists because the two problems rarely get solved together. The brands with the best shade ranges across depth and undertone are not usually the brands formulating for mature skin, and the ranges built around mature skin are frequently twelve shades that stop well short of deep. The result is a choice between a formula that behaves and a shade that matches, and that is not a choice anyone should have to make.
Three specific issues come up on mature deep skin and almost never get written about. Ashiness is the most common: a formula with a high mineral filter load — zinc oxide, titanium dioxide — leaves a cool white cast that reads gray on deep skin, and the effect is more visible once skin has lost some of its natural luminosity. Undertone collapse is the second: short ranges tend to get darker without getting warmer or cooler, so the deep shades all sit on one undertone and most people are matched to the nearest wrong one. Flashback is the third, where that same mineral load bounces camera flash and turns a photograph gray.
The fourth issue is specific to age rather than depth: pigmentation. Hyperpigmentation and post-inflammatory marks are common on deeper skin, and they need targeted concealing rather than a heavier foundation everywhere — the same principle as everywhere else on this site, applied to a concern that gets dismissed more often.
What to do with all of that: buy for undertone first, depth second, formula third. Depth can be adjusted slightly by mixing two shades. Undertone cannot be fixed, and a wrong-undertone match is what people mean when they say a foundation looked fine in the shop and wrong at home.
