Short answer: when choosing your extension colour online, compare mainly the mid-lengths and ends of your hair in natural light. The root may be darker, cooler or simply different from the area where the extensions will actually blend.
A perfect match does not always mean finding one code identical to the root. The aim is for the extension colour to disappear visually into the part of the hair with which it will actually be mixed.
Why is the root not always the best reference?
Natural colour can change through the lengths because of sun exposure, colouring, lightening, toning and simple regrowth. If the extensions begin below the root, the important area is the one that will remain visually in contact with the new lengths.
A useful photograph should therefore show the hair down, without filters, with a sufficiently wide view of the mid-lengths and ends.
Which light should you use to compare colour?
Indirect natural light is usually the most reliable reference. Very warm lighting, cool spotlights, flash and smartphone filters can significantly alter the perception of blondes, brunettes and undertones.
The screen itself is also a variable: brightness, colour temperature and calibration differ from one device to another. A photo or digital swatch is therefore useful for narrowing down the choice, but it cannot be treated as an absolute measurement.
What if the hair has balayage, highlights or several tones?
In that case, you do not necessarily need to chase a single uniform colour. It is often more natural to consider the overall visual blend: dominant colour, undertone through the lengths and brightness at the ends. Compatible shades can also be combined when the result requires depth and movement.
When is an in-person comparison useful?
When the difference between two shades is minimal, when the hair has complex undertones or when the colour work is highly dimensional, a physical comparison remains the most precise option. That is why VELVET Chart exists: a colour ring with more than 70 shades made from real hair, designed to show the actual colour outside a screen.
If you are choosing a system directly, first identify the right method in Human hair extensions: which method should you choose? and then select from the shades available for that specific line.
In summary
To choose a colour online: compare mid-lengths and ends, use natural light, avoid filters, review more than one photo and treat the screen as an approximation. When two shades are too close to distinguish confidently, a physical colour ring is more reliable than any display.