Qualia

Individual instances of subjective, conscious experience/perception. Examples of qualia include the perceived sensation of pain of a headache, the taste of carrots or the blueness of the sky.

While two individuals may be able to agree that a color they are both perceiving is red, and be perceiving the same reflected spectrum, the internalized perception of the two individuals could be vastly different. The Inverted Spectrum though experiment explores this concept.

A good resource for this concept is the video by VSauce: Is your red the same as my red?