While it's impossible to be 100% absolute, given variations in shades and undertones of the skin, and of any "problem" area to be camouflaged, this is nonetheless a good starting point.
To start with, please also reference here for more information on concealers and correctors (and here for MAC-specific information).
For the purpose of this post, it's assumed that you have fair-medium skin.
For blemish concealer, selecting the correct concealer is pretty straight-forward.
If you have a pink or yellow undertone to your skin:
- Red blemish: use a yellow toned concealer
- Non-red blemish: use a pink toned concealer
Basically, irrespective of the undertone of your skin, if the blemish is red, use a yellow-toned concealer to cover it.
To conceal pigmentation, you need to determine the shade of the pigmentation; for a lot of people, sun-damage pigmentation for example can be quite ashy looking; if this is the case, then you use a pink-toned concealer on top of it.
For port wine stains, a yellow toned concealer or (or a yellow corrector first, if it is very dark) will help to neutralise the red.
For redness found often around the nostrils or on the chin (or anywhere else), use a yellow toned concealer.
Under-eye concealer is a tiny bit more complicated, and rather than trying to explain it I'm going to include a flow-chart, which hopefully will help you to determine which concealer to use, and also if you need to use a corrector underneath your concealer.
First off, if you have a red undertone to your skin under your eye, then use a yellow toned concealer over these areas, regardless of your skin's undertone. For example a lot of people have some red just underneath the lower lash line, or at the outer corner of the eye.
In general, most people have some blue at the upper inner corner of their eye, where the eye meets the nose - this is because there's a vein that runs just underneath the skin at that point. In order to conceal this and any darkness directly underneath the eye, you need to know what colour concealer to use. To figure this out, you first need to know your skin's undertone, ie whether it's pink-based or more yellow-based, then take a look at this flowchart to see if you can determine which tone concealer you should be using.
|How to determine your under-eye concealer|