Make component colors configurable

scss/_card.scss

@@ -36,6 +36,7 @@
   // as much space as possible, ensuring footers are aligned to the bottom.
   flex: 1 1 auto;
   padding: $card-spacer-x;
+  color: $card-color;
 }
 
 .card-title {

scss/_dropdown.scss

@@ -25,7 +25,7 @@
   padding: $dropdown-padding-y 0;
   margin: $dropdown-spacer 0 0; // override default ul
   font-size: $dropdown-font-size;
-  color: $body-color;
+  color: $dropdown-color;
   text-align: left; // Ensures proper alignment if parent has it changed (e.g., modal footer)
   list-style: none;
   background-color: $dropdown-bg;

scss/_jumbotron.scss

@@ -1,6 +1,7 @@
 .jumbotron {
   padding: $jumbotron-padding ($jumbotron-padding / 2);
   margin-bottom: $jumbotron-padding;
+  color: $jumbotron-color;
   background-color: $jumbotron-bg;
   @include border-radius($border-radius-lg);
 

scss/_list-group.scss

@@ -47,6 +47,7 @@
   padding: $list-group-item-padding-y $list-group-item-padding-x;
   // Place the border on the list items and negative margin up for better styling
   margin-bottom: -$list-group-border-width;
+  color: $list-group-color;
   background-color: $list-group-bg;
   border: $list-group-border-width solid $list-group-border-color;
 

scss/_modal.scss

@@ -70,6 +70,7 @@
   flex-direction: column;
   width: 100%; // Ensure `.modal-content` extends the full width of the parent `.modal-dialog`
   // counteract the pointer-events: none; in the .modal-dialog
+  color: $modal-content-color;
   pointer-events: auto;
   background-color: $modal-content-bg;
   background-clip: padding-box;

scss/_toasts.scss

@@ -2,6 +2,7 @@
   max-width: $toast-max-width;
   overflow: hidden; // cheap rounded corners on nested items
   font-size: $toast-font-size; // knock it down to 14px
+  color: $toast-color;
   background-color: $toast-background-color;
   background-clip: padding-box;
   border: $toast-border-width solid $toast-border-color;

scss/_variables.scss

@@ -746,6 +746,7 @@ $dropdown-min-width:                10rem !default;
 $dropdown-padding-y:                .5rem !default;
 $dropdown-spacer:                   .125rem !default;
 $dropdown-font-size:                $font-size-base !default;
+$dropdown-color:                    $body-color !default;
 $dropdown-bg:                       $white !default;
 $dropdown-border-color:             rgba($black, .15) !default;
 $dropdown-border-radius:            $border-radius !default;
@@ -804,6 +805,7 @@ $pagination-disabled-border-color:  $gray-300 !default;
 // Jumbotron
 
 $jumbotron-padding:                 2rem !default;
+$jumbotron-color:                   null !default;
 $jumbotron-bg:                      $gray-200 !default;
 
 
@@ -817,6 +819,7 @@ $card-border-color:                 rgba($black, .125) !default;
 $card-inner-border-radius:          calc(#{$card-border-radius} - #{$card-border-width}) !default;
 $card-cap-bg:                       rgba($black, .03) !default;
 $card-cap-color:                    null !default;
+$card-color:                        null !default;
 $card-bg:                           $white !default;
 
 $card-img-overlay-padding:          1.25rem !default;
@@ -886,6 +889,7 @@ $toast-max-width:                   350px !default;
 $toast-padding-x:                   .75rem !default;
 $toast-padding-y:                   .25rem !default;
 $toast-font-size:                   .875rem !default;
+$toast-color:                       null !default;
 $toast-background-color:            rgba($white, .85) !default;
 $toast-border-width:                1px !default;
 $toast-border-color:                rgba(0, 0, 0, .1) !default;
@@ -924,6 +928,7 @@ $modal-dialog-margin-y-sm-up:       1.75rem !default;
 
 $modal-title-line-height:           $line-height-base !default;
 
+$modal-content-color:               null !default;
 $modal-content-bg:                  $white !default;
 $modal-content-border-color:        rgba($black, .2) !default;
 $modal-content-border-width:        $border-width !default;
@@ -982,6 +987,7 @@ $progress-bar-transition:           width .6s ease !default;
 
 // List group
 
+$list-group-color:                  null !default;
 $list-group-bg:                     $white !default;
 $list-group-border-color:           rgba($black, .125) !default;
 $list-group-border-width:           $border-width !default;

site/docs/4.2/getting-started/theming.md

@@ -75,7 +75,7 @@ With that setup in place, you can begin to modify any of the Sass variables and
 
 Every Sass variable in Bootstrap 4 includes the `!default` flag allowing you to override the variable's default value in your own Sass without modifying Bootstrap's source code. Copy and paste variables as needed, modify their values, and remove the `!default` flag. If a variable has already been assigned, then it won't be re-assigned by the default values in Bootstrap.
 
-You will find the complete list of Bootstrap's variables in `scss/_variables.scss`.
+You will find the complete list of Bootstrap's variables in `scss/_variables.scss`. Some variables are set to `null`, these variables don't output the property unless they are overridden in your configuration.
 
 Variable overrides within the same Sass file can come before or after the default variables. However, when overriding across Sass files, your overrides must come before you import Bootstrap's Sass files.