The paper proposes a novel approach to analyze the dichromatic color vision defects from a point of spectral responses based on the projection theory of spectral space to/from 2-D dichromatic Human Visual Sub-Space. The visible spectra to the dichromats (protanopes, deutanopes, and tritanopes) are extracted from an n-dimensional spectral input with the 2-D version of Matrix-R notated as R_dichro. Since the matrix R_dichro is an identical and invariant mapping operator inherent in human vision that is independent of any linear transformation or any illuminant, the fundamental spectra C*_dichro sensed with matrix R_dichro are also inherent in the dichromats. The lost spectra are easily obtained as a difference in the fundamentals between the normals and the the dichromats. These lost spectral profiles tell us why the color appearances are similar to the protanopes and deutanopes, and dissimilar to the tritanopes. The perceived colors are simulated based on the two hypotheses of substitution and nulling processes.