How make "color isolation" effect like in photoshop with java

I would like to know how to isolate a certain color in an image and set the rest to gray using java.

So far I managed to do so, but in a hardcode way by looping through all the pixels of the image and then checking the RGB values. I am using BufferedImage to load the image and the Color class to deal with RGB values.

The isColorRed checks if the color is red or not.

private static boolean isColorRed(Color color) {
    int red = color.getRed();
    int green = color.getGreen();
    int blue = color.getBlue();

    return ((red >= 70 && red <= 255) && (green >= 0 && green <= 80) && (blue >= 0 && blue <= 80));
}

The isolateColor method is responsible to set all pixels to grey except for the red ones.

private static void isolateColor(BufferedImage image) {

    int width = image.getWidth();
    int height = image.getHeight();

    for (int y = 0; y < height; y++) {
        for (int x = 0; x < width; x++) {

            Color c = new Color(image.getRGB(x, y));

            if (!isColorRed(c)) {
                int red = (int) (c.getRed() * 0.3);
                int green = (int) (c.getGreen() * 0.587);
                int blue = (int) (c.getBlue() * 0.114);

                int gray = red + green + blue;

                Color newColor = new Color(gray, gray, gray);
                image.setRGB(x, y, newColor.getRGB());
            } else {
                Color newColor = new Color(c.getRed(), c.getGreen(), c.getBlue());
                image.setRGB(x, y, newColor.getRGB());
            }

        }
    }

    File file;
    try {
        file = new File("src/grey.png");
        ImageIO.write(image, "png", file);
    } catch (IOException e) {
        System.out.println(e.getMessage());
    }
}

The original image :

After the treatment :

Is there any API built-in or external that can isolate one color or more in a single image