I need to convert an image to grey scale then colorize ranges of grey to new colors

I need my program to go through the pixels in an image, change them to grey scale. Then I need to take ranges of gray and colorize them using if - else and if-else-if statements. Can someone please help me figure this out? Here's my code so far:

import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.*;
import javax.imageio.ImageIO;
import javax.swing.JFrame;

public class Colorize {

    BufferedImage image;
    int width;
    int height;

    public Colorize()  {
        try {
            File input = new File("Grayscale.jpg");
            image = ImageIO.read(input);
            width = image.getWidth();
            height = image.getHeight();

            for(int i=0; i<height; i++){

                for(int j=0; j<width; j++){
                    int col = image.getRGB(i, j);
                    Color c = new Color(col, true);
                    int red = c.getRed();
                    int green = c.getGreen();
                    int blue = c.getBlue();
                    if ((red>= 1)&&(red<=30))  {
                        c = new Color(c.getRed() + 10, c.getGreen(), c.getBlue());
                    }
                    if ((red>= 31)&&(red<=60))  {
                        c = new Color(c.getRed(), c.getGreen() + 10, c.getBlue());
                    }
                    if ((red>= 61)&&(red<=90))  {
                        c = new Color(c.getRed(), c.getGreen(), c.getBlue() + 10);
                    }
                    if ((red>= 91)&&(red<=120))  {
                        c = new Color(c.getRed() + 10, c.getGreen() + 10, c.getBlue());
                    }
                    if ((red>= 121)&&(red<=150))  {
                        c = new Color(c.getRed() + 10, c.getGreen(), c.getBlue() + 10);
                    }
                    if ((red>= 151)&&(red<=180))  {
                        c = new Color(c.getRed(), c.getGreen() + 10, c.getBlue() + 10);
                    }
                    if ((red>= 181)&&(red<=210))  {
                        c = new Color(c.getRed() - 10, c.getGreen(), c.getBlue());
                    }
                    if ((red>= 211)&&(red<=240))  {
                        c = new Color(c.getRed(), c.getGreen() - 10, c.getBlue());
                    }
                    else {
                        c = new Color(c.getRed(), c.getGreen(), c.getBlue());
                    }
                    Color newColor = new Color(red+green+blue,red+green+blue,red+green+blue);
                    image.setRGB(j,i,newColor.getRGB());
                }
            }

            File output = new File("Colorize.jpg");
            ImageIO.write(image, "jpg", output);

        } catch (Exception e) {}
    }

    static public void main(String args[]) throws Exception 
    {
        Colorize obj = new Colorize();
    }
}