[ 1 ]          color    * normal *    deuteranopia    protanopia     tritanopia 
                 =====   ============   ============   ============   ============
                  C1       #000000        #000000        #000000        #000000   
                  C2       #585858        #585858        #585858        #585858   
                  C3       #989898        #989898        #989898        #989898   
                  C4       #ffffff        #ffffff        #ffffff        #ffffff   

                            normal      deuteranopia    protanopia     tritanopia 
                         ============   ============   ============   ============
  pairs         lowest --   25.335194 --   25.335194 --   25.335194 --   25.335194
=========           |    ------------   ------------   ------------   ------------
C3 vs. C4 |  25.335194   #  25.335194   #  25.335194   #  25.335194   #  25.335194
C2 vs. C3 |  25.435704   *  25.435704   *  25.435704   *  25.435704   *  25.435704
C1 vs. C2 |  25.537647   *  25.537647   *  25.537647   *  25.537647   *  25.537647
C2 vs. C4 |  49.176253   *  49.176253   *  49.176253   *  49.176253   *  49.176253
C1 vs. C3 |  49.446049   *  49.446049   *  49.446049   *  49.446049   *  49.446049
C1 vs. C4 | 100.000001   * 100.000001   * 100.000001   * 100.000001   * 100.000001