Colour is a very broad area of study. Here is a little handy reference to some colour terms.
Additive Colour Model: A system involving light that starts with no light (black) and creates coloured light as wavelengths are added; the end-point is white, when all wavelengths of visible light are present. The primary colours in the additive system are red, green and blue, which create white light when combined together at equal intensities. Combining the primaries, creates secondary colours of cyan, magenta and yellow. In the additive system, the more colours that are added, the lighter the result is and is closer to white. Additive colour is the system used in televisions and computer monitors.
Chromaticity or Chroma: This concept is related to Saturation but refers to the purity of the colour. Highly chromatic colours have little or no “impurities” like black, white or grey and appear very clear and vivid.
Chroma is can also be thought of as how “colourful” a colour is; how much of the pure hue is in the colour. Colours with the maximum chroma are those that do not have any black or white in them. With most hues, as the colour gets brighter, the chroma increases (not with very light colours).
Colours without any hue are monochromatic or achromatic and will look grey.
Hue: The actual colour the human eye sees and is caused by wavelengths of light. In the case of an object, the predominant wavelength that is reflected from the object is perceived as the hue (e.g. a red rose appears to the eye as “red” because that wavelength is not being absorbed by the petals, it is being bounced back – all other wavelengths of the spectrum pass through it and are not visible to the eye). In the case of light, the wavelength that is being emitted is what the eye perceives.
RYB Colour Model: The red-yellow-blue system is the traditional set of primary colours. These colours form another subtractive model predating the CYM model, and became the basis for theories of colour in the 18th century. When these primaries are mixed, secondary colours of green, orange and violet are created. The RYB model is still the standard that most people are taught and is the basis of the Itten colour wheel.
Saturation: Related to the concept of Chromaticity, saturation indicates how intense a colour will appear in different lighting conditions. It is basically comparing a colour to its own brightness. Instead of thinking of saturation in terms of “light” and “dark.” it’s better to think of it in terms of “weak” and “strong” or “pale” and “pure.”
Shade: When a pure colour is mixed with black to produce darker colours.
Spectrum (of visible light): The range of electromagnetic waves perceived as colours by the human eye when white light is split through a prism. Violet is the shortest wavelength and red is the longest wavelength, so the colours in spectral order are violet, blue, green, yellow, orange, and red. Visible light ranges from ultra-violet (as wavelengths get smaller above ultra-violet, they become x-ray and gamma ray) to infrared (as wavelengths get larger below infrared, they become microwave and radio waves).
Subtractive Colour Model: The system used in the mixing of paints, inks, dyes, films and other colorants to create a vast range of colours. The subtractive system starts with white light and color is created as paints, pigments or transparent films are placed on a reflective surface* (such as white paper) or in front of a light source, and have the effect of subtracting wavelengths from the white light. The primary colours in the subtractive system are cyan, magenta and yellow. When these are mixed, they produce secondary colours of red, green and blue. When all are mixed at equal intensities, the result is black.
[*The human eye will perceive the reflected wavelengths as colour, not the wavelengths that are absorbed by the colorants.]
Tonal Family: Pure colours can be mixed with black, white, and grey to create a tonal family. (See Shades, Tints, Tones)
Tint: When a pure colour is mixed with white to produce lighter colours.
Tone: When a pure colour is mixed with grey to produce more muted colours.
Value: Property of colour that is intrinsically the same as “brightness.” Value describes how “dark” or “light” a colour is based on how much light is emanating from it or how close to white it is.