gnome-shell/data/theme/gnome-shell-sass/widgets/_screenshot.scss

// Screenshot UI
.icon-label-button-container {
  spacing: $base_spacing;
  font-size: $base_font_size - 3pt;

  StIcon {
    icon-size: 32px;
  }
}

.screenshot-ui-panel {
  background-color: $osd_bg_color;
  border-radius: 12px + 21px;
  padding: 18px;
  padding-bottom: 18px - 6px;
  margin-bottom: $base_margin * 8;
  spacing: $base_padding * 2;
}

.screenshot-ui-close-button {
  background-color: $osd_bg_color;
  border-radius: 99px;
  width: 64px;
  height: 64px;
  margin: 64px;

  &:hover, &:focus { background-color: $hover_bg_color; }
  &:active { background-color: $active_bg_color; }
  &:checked { background-color: darken($osd_bg_color, 5%); }

  StIcon {
    icon-size: $base_icon_size * 2;
  }
}

.screenshot-ui-type-button {
  padding: $base_padding * 2 $base_padding * 3;
  border-radius: 12px + 21px - 18px;
  font-weight: bold;
  &:hover, &:focus { background-color: $hover_bg_color; }
  &:active { background-color: $active_bg_color; }
  &:checked { background-color: $hover_bg_color; }
  &:insensitive { color: $insensitive_fg_color; }
}

.screenshot-ui-capture-button {
  width: 36px;
  height: 36px;
  border-radius: 99px;
  border: 4px white;
  padding: 4px;

  .screenshot-ui-capture-button-circle {
    background-color: white;
    transition-duration: 200ms;
    &:hover, &:focus { background-color: $hover_bg_color; }
    border-radius: 99px;
  }

  &:hover, &:focus {
    .screenshot-ui-capture-button-circle {
      background-color: darken(white, 15%);
    }
  }

  &:active {
    .screenshot-ui-capture-button-circle {
      background-color: darken(white, 50%);
    }
  }
}

.screenshot-ui-area-indicator-shade {
  background-color: rgba(0, 0, 0, .3);
}

.screenshot-ui-area-selector {
  .screenshot-ui-area-indicator-shade {
    background-color: rgba(0, 0, 0, .5);
  }

  .screenshot-ui-area-indicator-selection {
    border: 2px white;
  }
}

.screenshot-ui-area-selector-handle {
  border-radius: 99px;
  background-color: white;
  box-shadow: 0 1px 3px 2px rgba(0, 0, 0, 0.2);
  width: 24px;
  height: 24px;
}

.screenshot-ui-window-selector {
  background-color: $system_bg_color;

  .screenshot-ui-window-selector-window-container {
    margin: 100px;
  }

  &:primary-monitor {
    .screenshot-ui-window-selector-window-container {
      // Make some room for the panel.
      margin-bottom: 200px;
    }
  }
}

.screenshot-ui-window-selector-window-border {
  transition-duration: 200ms;
  border-radius: 18px;
  border: 6px transparent;
}

.screenshot-ui-window-selector-window {
  &:hover {
    .screenshot-ui-window-selector-window-border {
      border-color: darken($selected_bg_color, 15%);
    }
  }
  &:checked {
    .screenshot-ui-window-selector-window-border {
      border-color: $selected_bg_color;
      background-color: transparentize($selected_bg_color, 0.8);
    }
  }
}

.screenshot-ui-screen-selector {
  transition-duration: 200ms;
  background-color: rgba(0, 0, 0, .5);

  &:hover { background-color: rgba(0, 0, 0, .3); }
  &:active { background-color: rgba(0, 0, 0, .7); }
  &:checked {
    background-color: transparent;
    border: 2px white;
  }
}