Поправил имя переменной с цветом второстепенного текста

src/blocks/field-actions/field-actions.scss

@@ -12,7 +12,7 @@
     margin-top: $typo-margin-vertical;
     margin-bottom: $typo-margin-vertical;
     font-size: $font-size-sm;
-    color: $text-color--muted;
+    color: $text-color-muted;
     line-height: 1.2em;
   }
 }

src/blocks/table-responsive/table-responsive.scss

@@ -17,7 +17,7 @@
     padding: 0.4em $field-padding-horizontal;
     font-size: $font-size-sm;
     line-height: 1em;
-    color: $text-color--muted;
+    color: $text-color-muted;
   }
 
   td,

src/blocks/table/table.scss

@@ -32,6 +32,6 @@
   //   border-bottom: 1px solid $border-color;
   //   font-size: $font-size-sm;
   //   line-height: 1em;
-  //   color: $text-color--muted;
+  //   color: $text-color-muted;
   // }
 }

src/blocks/tabs/tabs.scss

@@ -38,7 +38,7 @@
     position: relative;
     margin: 0 0.3em 0.3em 0;
     border: 1px solid $border-color;
-    color: $text-color--muted;
+    color: $text-color-muted;
 
     @media (min-width: $screen-md) {
       margin: 0;

src/scss/mixins/form-mixins.scss

@@ -36,7 +36,7 @@
   }
 
   &::placeholder {
-    color: $text-color--muted;
+    color: $text-color-muted;
     opacity: 1;
   }
 }
@@ -47,7 +47,7 @@
   padding-top: 0.4em;
   font-size: $font-size-sm;
   line-height: 1.2em;
-  color: $text-color--muted;
+  color: $text-color-muted;
 
   &:empty { // stylelint-disable-line
     display: none;

src/scss/variables.scss

@@ -27,7 +27,7 @@ $color-gh:                    #24292e;
 // Семантические цвета
 
 $text-color:                  $gray-darkest;
-$text-color--muted:           $gray;
+$text-color-muted:            $gray;
 $body-bg:                     $white;
 
 $link-color:                  $color-main;