private static float @NotNull [] rgbDiffColor(@NotNull Color c1, @NotNull Color c2) {
    return new float[] {
      c1.getRed() - c2.getRed(),
      c1.getGreen() - c2.getGreen(),
      c1.getBlue() - c2.getBlue()
    };
  }
private static float @NotNull [] rgbDiffColor(@NotNull Color c1, @NotNull Color c2)