Objects do not physically change the wavelength of light. The color of an object is determined by the interaction of light with the object's surface. When light strikes an object, it can be absorbed, transmitted, or reflected.
The atoms or molecules of an object interact with the incoming light waves. These interactions can result in the absorption of certain wavelengths of light and the reflection or transmission of others. The absorbed light energy can be converted into other forms, such as heat.
The color we perceive an object to have is determined by the wavelengths of light that are reflected (or transmitted) by the object. For example, an object that appears red absorbs most of the wavelengths of light except for those corresponding to red, which are reflected. Similarly, an object that appears blue absorbs most wavelengths except for those corresponding to blue.
It's important to note that the color of an object is dependent on the wavelengths of light that are incident upon it and the interaction of those wavelengths with the object's surface. Objects themselves do not physically alter the wavelengths of light; they selectively interact with different wavelengths, leading to the perception of different colors.