You may want to skip this post. There will be no concrete answer at the end. It will be a thought repository for my ramblings till someone helps me understand this.
Traditionally, undertones are thought to be either cool, neutral, or warm, not coloured.
Overtones are the outside colour of the skin, like the names of foundation, as porcelain, bisque, buff, natural, warm beige, and so on. Light/medium/deep also refers to overtones. The overtone must be in the top epidermal layer.
You can get any combination of undertone and overtone. So warm undertone + ivory overtone, or cool undertone + ebony overtone, etc. Porcelain and ebony overtones can share the same cool undertone.
Worth noting too is that you can have a false overtone. The red flush in the skin of women with too-yellow hair, or the yellow overtone in the cool dark Seasons when they wear too-warm colour, these are just effects created by wrong colour. They clear away as soon as you change your shirt or hair colour.
Where is the undertone and what exactly is this colour that we are calling cool-neutral-warm?
I looked for input from respected sources.
1. Bernice Kentner of Color Me A Season, always ahead of her time, describes undertone as a real colour, a combination of 4 variables. From her book, The Magnificent Eye, she describes undertone as the result of an equation made up of 4 variables:
. the thickness of the skin which varies by Season and determines which colours show through
. the yellow-brown colour of all skin, beneath the top layer
. the meshwork of oxygenated (red) and non-oxygenated (blue) blood vessels beneath the skin
. the velocity of blood flow in those vessels; so Autumn has faster blood flow which shows more red of arterial blood
I do not know about the blood flow velocity. I would think that ultrasound would have detected those differences among people.
I absolutely agree with her that Seasonal Colour Analysis is not about overtones. If it were, yellow skin would wear warm foundation, but it often does not (or should not). If it were, wearing our skin colour would be flattering but it isn’t. The apparent surface skin colour does not appear in the swatch books for the 12 Seasons because surface colour is not a good representation of our true pigmentation.
2. Lauren Battistini at Color My Closet makes the fundamentally important point in this post, that undertone refers to how skin reacts to colour. If your skin is most perfected by cool colours, then your undertone is cool. Not certain if I can extrapolate this far, but maybe this means that undertone is not a real colour at all, and could not be found anywhere in the biological layers of skin. It is a reactionary term.
Personal Colour Analysis is about identifying the precise degree of darkness, warmth, and saturation in the colours of your body, and so in the colours that harmonize with your native colours when you wear them. It has nothing to do with overtone really, which is why suntans and rosacea do not affect the PCA result. Those are surface effects. The PCA process looks through the surface skin layer to evaluate reactions in the lower layers.
In the Comments, Lauren says that each Season has a core colour, using the example that Autumn is orange. Each Season does have a signature or core colour (Winter=red, Summer=blue, Spring=yellow). This overlaps with the undertone concept but isn’t exactly the same.
3. Imogen Lamport at Inside Out Style Blog writes an excellent blog with practical real-world advice. In this post on skin tone and makeup, a client writes in with a question. Imogen offers several examples from her experience as a colour analyst.
If I understand this right,
Now you may be more obvious and have a warm yellow or goldish undertone and overtone and therefore warm colouring, or you may have a pinkish undertone and overtone and be cool.
This means that the True Seasons are those where overtone and undertone accord. She cites examples where the two may conflict but I remain confused.
4. Beauty School Blog is written by makeup artist, Jen. I find it a fresh take on makeup blogs, with good lessons, a genuine voice, and a wider spectrum of topics. I found this article very thorough. If the undertone is a real colour, then which colour is it exactly, and where is it?
5. Variations of the pigments. There are certainly different colours of melanin and carotene. How about hemoglobin? Do different people have different coloured blood? I have never heard a surgeon say this (not counting the different colours of venous and arterial blood). To the naked eye, I can tell you that dogs and cats have the same colour of blood. How much can the pigmentation of a hemoglobin molecule be altered without affecting its ability to carry oxygen, certainly a life-threatening event that evolution might not have permitted. I have only questions at this point.
6. The 12B concept of undertones. The pictures posted along this article show how undertones appear in my head. There is no scientific testing here, only what I see when I look at this skin. (Dark Autumn could be redder. Bright Winter could be lighter and yellower. Light Summer, I couldn’t decide. Close enough to make the point.)
What use is it?
Foundation is matched to undertone (cool/neutral/warm) and overtone (ivory to ebony).
For some, these are the fundamental lip and blush colours, the from-within, most intrinsic colours. Using them for items such as eyeglass frames, ties, scarves, and accessories looks good, though the viewer would never know why.