node_modules/@covalent/core/expansion-panel/_expansion-panel-theme.scss

@import '../common/styles/variables';
@import '../common/styles/elevation';
@import '../common/styles/theme-functions';
@import '../common/styles/typography-functions';

@mixin td-expansion-panel-typography($config) {
  .td-expansion-label {
    font: {
      family: td-font-family($config);
      size: td-font-size($config, subheading-2);
      weight: td-font-weight($config, subheading-2);
    }
  }
  .td-expansion-sublabel {
    font: {
      family: td-font-family($config);
      size: td-font-size($config, body-1);
      weight: td-font-weight($config, body-1);
    }
  }
}

@mixin td-expansion-panel-theme($theme) {
  $accent: map-get($theme, accent);
  $warn: map-get($theme, warn);
  $foreground: map-get($theme, foreground);
  $background: map-get($theme, background);

  .td-expansion-panel-group {
    .td-expansion-panel {
      transition: 120ms ease-in;
      &:not(:last-of-type) {
        &.td-expanded {
          margin-bottom: $margin;
        }
      }
      &:not(:first-of-type) {
        &.td-expanded {
          margin-top: $margin;
        }
      }
    }
  }

  .td-expansion-panel {
    @include mat-elevation(1);

    background-color: mat-color($background, card);
    .td-expansion-panel-header {
      &:focus:not(.mat-disabled),
      &:hover:not(.mat-disabled) {
        background: mat-color($background, 'hover');
      }
      .td-expansion-panel-header-content {
        mat-icon.td-expand-icon {
          color: mat-color($foreground, icon);
        }
        &.mat-disabled {
          &,
          & * {
            color: mat-color($foreground, disabled);
          }
        }
      }
    }
    mat-icon.td-expand-icon {
      color: mat-color($foreground, icon);
    }
    .td-expansion-label,
    .td-expansion-sublabel {
      &,
      & * {
        vertical-align: middle;
      }
    }
    .td-expansion-sublabel {
      color: mat-color($foreground, secondary-text);
    }
  }
}