The three dimensions of colour
Every colour comes down to three things: hue (the colour family, like red, blue, green), value (how light or dark it is), and chroma (how pure or muted it is). In seasonal analysis we mostly care about value and chroma, plus the temperature (warm or cool) of the hue. Once these click, you'll see why some colours lift your face and others drag it down.
Hue and temperature
Hue is the pure colour, red, yellow, blue and so on. Nearly every hue (bar pure orange and pure blue) can lean warm or cool. Warm colours carry yellow undertones, cool ones carry blue. Tomato red is warm, for instance, while raspberry red is cool.
Value in practice
Value is just how light or dark a colour looks. Navy and powder blue are the same hue at different values. Your best value range ties to your natural contrast, the gap between your hair, skin, and eyes.
Chroma
Chroma is colour purity. High-chroma colours are clear and vibrant (think jewel tones), low-chroma colours are muted or dusty (sage green versus kelly green). Your natural chroma decides whether clear or soft colours suit you best.

