node_modules/@covalent/core/file/_file-theme.scss

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

@mixin td-file-theme($theme) {
  $background: map-get($theme, background);

  td-file-upload {
    .td-file-upload-cancel {
      mat-icon {
        background-color: mat-color($background, background);
      }
    }
  }
  td-file-input {
    /**
    * Class that is added ondragenter by the [TdFileDrop] directive.
    */
    .drop-zone {
      transition: background $swift-ease-out-duration $swift-ease-out-timing-function,
        mat-elevation-transition-property-value();
      @include mat-elevation(8);
    }
  }
}