private static @Nullable Integer getScrollbarAlpha(ColorKey colorKey) {
    if (!LoadingState.CONFIGURATION_STORE_INITIALIZED.isOccurred() || !UISettings.getInstance().getUseContrastScrollbars()) {
      return null;
    }

    final var contrastElementsKeys = List.of(
      ScrollBarPainter.THUMB_OPAQUE_FOREGROUND,
      ScrollBarPainter.THUMB_OPAQUE_BACKGROUND,
      ScrollBarPainter.THUMB_OPAQUE_HOVERED_FOREGROUND,
      ScrollBarPainter.THUMB_OPAQUE_HOVERED_BACKGROUND,
      ScrollBarPainter.THUMB_FOREGROUND,
      ScrollBarPainter.THUMB_BACKGROUND,
      ScrollBarPainter.THUMB_HOVERED_FOREGROUND,
      ScrollBarPainter.THUMB_HOVERED_BACKGROUND
    );

    if (!contrastElementsKeys.contains(colorKey)) {
      return null;
    }

    int lightAlpha = SystemInfo.isMac ? 120 : 160;
    int darkAlpha = SystemInfo.isMac ? 255 : 180;
    int alpha = Registry.intValue("contrast.scrollbars.alpha.level");
    if (alpha > 0) {
      return Integer.min(alpha, 255);
    }

    return UIUtil.isUnderDarcula() ? darkAlpha : lightAlpha;
  }
private static @Nullable Integer getScrollbarAlpha(ColorKey colorKey)