node_modules/@angular/material/tabs/_tabs-theme.scss

@import '../core/theming/palette';
@import '../core/theming/theming';
@import '../core/typography/typography-utils';

@mixin mat-tabs-color($config-or-theme) {
  $config: mat-get-color-config($config-or-theme);
  $primary: map-get($config, primary);
  $accent: map-get($config, accent);
  $warn: map-get($config, warn);
  $background: map-get($config, background);
  $foreground: map-get($config, foreground);
  $header-border: 1px solid mat-color($foreground, divider);

  .mat-tab-nav-bar,
  .mat-tab-header {
    border-bottom: $header-border;
  }

  .mat-tab-group-inverted-header {
    .mat-tab-nav-bar,
    .mat-tab-header {
      border-top: $header-border;
      border-bottom: none;
    }
  }

  .mat-tab-label, .mat-tab-link {
    color: mat-color($foreground, text);

    &.mat-tab-disabled {
      color: mat-color($foreground, disabled-text);
    }
  }

  .mat-tab-header-pagination-chevron {
    border-color: mat-color($foreground, text);
  }

  .mat-tab-header-pagination-disabled .mat-tab-header-pagination-chevron {
    border-color: mat-color($foreground, disabled-text);
  }

  // Remove header border when there is a background color
  .mat-tab-group[class*='mat-background-'] .mat-tab-header,
  .mat-tab-nav-bar[class*='mat-background-'] {
    border-bottom: none;
    border-top: none;
  }

  .mat-tab-group, .mat-tab-nav-bar {
    $theme-colors: (
      primary: $primary,
      accent: $accent,
      warn: $warn
    );

    @each $name, $color in $theme-colors {
      // Set the foreground color of the tabs
      &.mat-#{$name} {
        @include _mat-tab-label-focus($color);
        @include _mat-ink-bar($color);

        // Override ink bar when background color is the same
        &.mat-background-#{$name} {
          > .mat-tab-header, > .mat-tab-link-container {
            @include _mat-ink-bar($color, default-contrast);
          }
        }
      }
    }

    @each $name, $color in $theme-colors {
      // Set background color of the tabs and override focus color
      &.mat-background-#{$name} {
        @include _mat-tab-label-focus($color);
        @include _mat-tabs-background($color);
      }
    }
  }
}

@mixin _mat-ink-bar($color, $hue: default) {
  .mat-ink-bar {
    background-color: mat-color($color, $hue);
  }
}

@mixin _mat-tab-label-focus($tab-focus-color) {
  .mat-tab-label,
  .mat-tab-link {
    &.cdk-keyboard-focused,
    &.cdk-program-focused {
      &:not(.mat-tab-disabled) {
        background-color: mat-color($tab-focus-color, lighter, 0.3);
      }
    }
  }
}

@mixin _mat-tabs-background($background-color) {
  // Note that these selectors target direct descendants so
  // that the styles don't apply to any nested tab groups.

  // Set background color for the tab group
  > .mat-tab-header, > .mat-tab-link-container, > .mat-tab-header-pagination {
    background-color: mat-color($background-color);
  }

  // Set labels to contrast against background
  > .mat-tab-header .mat-tab-label, > .mat-tab-link-container .mat-tab-link {
    color: mat-color($background-color, default-contrast);

    &.mat-tab-disabled {
      color: mat-color($background-color, default-contrast, 0.4);
    }
  }

  // Set pagination chevrons to contrast background
  > .mat-tab-header-pagination .mat-tab-header-pagination-chevron,
  > .mat-tab-links .mat-focus-indicator::before,
  > .mat-tab-header .mat-focus-indicator::before {
    border-color: mat-color($background-color, default-contrast);
  }

  > .mat-tab-header-pagination-disabled .mat-tab-header-pagination-chevron {
    border-color: mat-color($background-color, default-contrast, 0.4);
  }

  // Set ripples color to be the contrast color of the new background. Otherwise the ripple
  // color will be based on the app background color.
  > .mat-tab-header .mat-ripple-element,
  > .mat-tab-link-container .mat-ripple-element {
    background-color: mat-color($background-color, default-contrast, 0.12);
  }
}

@mixin mat-tabs-typography($config-or-theme) {
  $config: mat-get-typography-config($config-or-theme);
  .mat-tab-group {
    font-family: mat-font-family($config);
  }

  .mat-tab-label, .mat-tab-link {
    font: {
      family: mat-font-family($config, button);
      size: mat-font-size($config, button);
      weight: mat-font-weight($config, button);
    }
  }
}

@mixin _mat-tabs-density($config-or-theme) {}

@mixin mat-tabs-theme($theme-or-color-config) {
  $theme: mat-private-legacy-get-theme($theme-or-color-config);
  @include mat-private-check-duplicate-theme-styles($theme, 'mat-tabs') {
    $color: mat-get-color-config($theme);
    $density: mat-get-density-config($theme);
    $typography: mat-get-typography-config($theme);

    @if $color != null {
      @include mat-tabs-color($color);
    }
    @if $density != null {
      @include _mat-tabs-density($density);
    }
    @if $typography != null {
      @include mat-tabs-typography($typography);
    }
  }
}