Why do object reflect or object particular color of light? Can anyone give an explanation of by comparing wavelengths?
Color is not a single valued variable as far as language goes. Color is the perception of the observer . The frequencies of the rainbow, do raise the perception of colors that one labels from red to violet and these have a one to one correspondence with the frequency of the light. But light reflected from an object can be a combination of frequencies that will give to the retina of the eye the signal "red" while not having the rainbow frequency "red".
In general white light ( all frequencies) falling on an object will be partially absorbed for some frequencies and the rest of the frequencies reflected, and the color itself that the observer records depends on biological perception , not clear cut one to one correspondence with frequency.
Now if by "color" you meant a single frequency, the perceived color of the object under monochromatic light will not be the same as with white light. Depending on the molecules and the percentage of absorption the object will be perceived as a hue of the incoming single frequency, unless the incoming frequency can raise the molecular levels high enough so that deexcitation will radiate a different frequency or combination of frequencies.
It is to do with the interaction of the incoming light and the molecules which make up the object.
A good example is a green leaf which has chlorophyll inside it.
The job of the chlorophyll is to absorb light which is then used by a plant as a source of energy.
When white light is incident on chlorophyll, the chlorophyll absorbs predominantly blue light with a little red and re-radiates very little. That is the light which is the source of energy for the plant.
So what happens to the incident green light?
Well it is absorbed but then most of it is re-radiated and that is why you see the leaf as being green.