Short answer
Colour is not a property of objects. It is what the visual system produces from light: a surface reflects some wavelengths more than others, three types of receptor in the eye respond differently to that mix, and the brain turns those three responses into the single sensation we call a colour. Change the light, the receptors or the surrounding scene and the colour changes, even though the object has not.
Visible light is a narrow band of electromagnetic radiation — roughly 380 to 700 nanometres in wavelength, sitting between ultraviolet and infrared. Nothing about a wavelength is inherently red or blue; a wavelength is simply a physical measurement, in the same way a frequency of air pressure variation is not inherently a musical note. What arrives at the eye from any real surface is almost never a single wavelength but a mixture: a distribution describing how much energy is present at each wavelength. That distribution is called the spectral power distribution, and it is the actual physical stimulus behind every colour you have ever seen.
This is why the same object can look different under different lights. The object's reflectance has not changed; the light being reflected has.
Most everyday colour is reflected colour. A surface absorbs some of the light falling on it and reflects the rest, and what it reflects is what reaches you. A lemon looks yellow because its skin absorbs most short-wavelength light and reflects most long and medium wavelengths — not because it contains something yellow in any deeper sense. Emitted colour works differently: a screen, a flame or an LED produces light rather than reflecting it, which is why screen colour and paint colour behave so differently and why a colour that looks right on a display can be impossible to reproduce in ink.
The human retina has three types of cone photoreceptor, each most sensitive to a different part of the spectrum — loosely long, medium and short wavelengths. Any incoming spectral distribution, however complicated, is reduced to just three numbers: how strongly each cone type responded. Everything you can see is reconstructed from those three signals. This is a drastic compression, and it has a striking consequence: completely different spectral distributions can produce identical cone responses, and therefore look identical, while being physically quite different lights.
That collapse is the reason two fabrics can match in the shop and clash in daylight — the phenomenon known as metamerism.
Cone responses are not the end of the process. Signals are recombined into opponent channels — roughly red-versus-green, blue-versus-yellow and light-versus-dark — before travelling to the brain, and the visual system then interprets them relative to everything else in view. It discounts the colour of the illumination, exaggerates differences at edges, and adapts continuously to whatever it has been looking at. The colour you experience is the output of that interpretation, not a direct readout of the light. This is why colour is best described as a perception with a physical cause, rather than as a physical property in its own right.
Wavelength ranges and perceptual thresholds are given as approximations: both vary between individuals and with viewing conditions, and sources differ on exact boundaries. Where a figure is contested or unavailable, this page says so rather than picking one.