Distinguish between tints, tones, and shades. How does each color modification change the original color's val

Answer 1

Light is a stream of photons, packets of electromagnetic energy, each at a specific wavelength and corresponding frequency and energy. Spectral analysis can quantify this quite accurately and consistently. That's the light reaching your eye and my eye.

Human optical receptors are sensitive at three separate wavelengths. Other animals can have more or fewer separate detection wavelengths. Color perception is done by the brain by comparing the relative response of the three sets of color receptors. This is why two lasers are enough to generate a full-color hologram. Some animals have color receptors in the infrared or ultraviolet, letting them visually distinguish things humans can't.

All humans with functioning color vision can distinguish colors in the human-visible spectrum with approximately equal ability. Some, by practice, have refined that skill. They have enhanced their visual cortex of the brain but not changed the optical receptors of the eye. Visual artists tend to do this. This part of vision is still objective, and can be tested and compared.

Now that you're thinking of color as a spectrogram instead of an RGB value, we can talk about these terms. So, your (undefined) term 'color val' is really a reference to a spectrogram. Tint is generally used of 'light' colors like pink, where shade is used of 'dark' colors. These terms would be used of materials with high or low reflectance values, respectively.

Tone is less often used to refer to color. When someone speaks of a skin tone or an earth tone, here's what a science definition might look like. A material whose color would be described as a 'skin tone' is one whose spectral composition is close enough to those commonly found in (human) skin that most people would think of skin when they saw it.

Answer 2

A tint is when white is added to the original color, lighter
A shade is when black is added to the original color, darker
Tone generally refers to the original color or how we perceive it.