Why does SVG desaturate the mask?

Question

HTML

<svg version="1.1" x="0px" y="0px"
             viewBox="0 0 1047.7 1323.45" style="width: 360px;" xml:space="preserve">
          <style type="text/css">
            .st0{mask: url(#masking-lum);}
            .st1{fill:#C6C6C6;}
            .st2{fill:#9D9D9C;}
            .st3{fill:#F9EEE6;}
            .st4{fill:none;stroke:#000000;stroke-width:5;stroke-miterlimit:10;}
          </style>
          <mask id="masking-lum" x="0" y="0">
              <image xlink:href="pattern-2312528_960_720.png" width="1047.7" height="1323.45" />
          </mask>
          <g id="Слой_1">
          </g>
          <g id="простынь">
            <path class="st0" d="M877.47,683.36h-720c-18.54,0-33.7-15.17-33.7-33.7V171.7c0-18.54,15.17-33.7,33.7-33.7h720
              c18.54,0,33.7,15.17,33.7,33.7v477.96C911.17,668.2,896.01,683.36,877.47,683.36z"/>
          </g>
          <g id="подушка_1">
            <path class="st1" d="M490.92,210.51c1.53-84.26,15.32-121.79,5.62-121.91c-9.7-0.13-24,19.28-173.11,21.83
              c-149.11,2.55-176.43-26.81-186-19.79c-7.05,5.17-0.38,55.53,10.34,103.02s-10.21,154.72-3.06,161.87
              c7.15,7.15,63.32-28.09,184.34-28.6c121.02-0.51,164.94,25.02,175.15,21.96C514.41,345.83,489.39,294.77,490.92,210.51z"/>
          </g>
          <g id="подушка_2">
            <path class="st1" d="M881.38,249.94c8.76-83.81,25.72-120.02,16.06-120.98c-9.66-0.96-25.57,17.14-174.34,6.89
              c-148.78-10.26-173.47-41.86-183.61-35.68c-7.47,4.55-5.15,55.29,1.46,103.53s-23.46,153.28-16.95,161.01
              c6.51,7.74,65.5-22.55,186.11-12.66c120.62,9.88,162.18,39.09,172.62,36.91S872.62,333.75,881.38,249.94z"/>
          </g>
          <g id="одеяло">
            <path class="st2" d="M844.92,591.83c-84.64-13.4-675-102.83-707.74-108.57s-37.91,2.3-37.91,21.26c0,18.96,0,45.06,0,45.06
              c0,12.07,0.1,17.89,6.16,22.26c-1.02,4.08-1.56,8.34-1.56,12.72V1182c0,29.07,23.78,52.85,52.85,52.85h720
              c29.07,0,52.85-23.78,52.85-52.85V798.26c0,0,16.08,10.21,16.08,0s0-104.94,0-140.94S929.56,605.23,844.92,591.83z"/>
          </g>
<g id="контуры"> ...</g>
          </svg>

Here is the SVG image code why is the mask desaturating? Tell me please!

Answer 1

Because the mask, by definition, only specifies the level of transparency, not the color.