Why are some solutions seen by the human eye with specific colors, while other solutions are observed to be colorless??

Answer 1

I am not certain of your question.
The first thing to note is in the dark, they do not have color.
The second thing to note, and ask, does the color of the solution change when radiated with different wavelengths of light?

The color you see coming from the solution can be light that is reflected, or diffused, or re-radiation of energy which impinged at a different wavelength.

On the diffusion of light, remember that short wavelength (such as blue) are "bent" or diffused more than the reds.

Remember, many elements have d-orbitals that are sensitive to specify impinging wavelength..if the electrons are excited, when they return to ground state, they can appear to emit light. Transition elements in solution are often in this category.

The answers to your question are complex, and you really should ask it about specific solutes. Life is generally not simple.