Java Bukkit error

package me.oostgames.disco;

import java.util.Random;

import org.bukkit.Bukkit;
import org.bukkit.Color;
import org.bukkit.Material;
import org.bukkit.entity.Player;
import org.bukkit.inventory.ItemStack;
import org.bukkit.inventory.meta.LeatherArmorMeta;
import org.bukkit.plugin.java.JavaPlugin;


public class DiscoArmor extends JavaPlugin {

	 public void onEnable() {
         Bukkit.getServer().getScheduler().scheduleSyncRepeatingTask(this, new Runnable() {
                 private Random r = new Random();
                
                 public void run() {
                         Color c = Color.fromRGB(r.nextInt(255), r.nextInt(255), r.nextInt(255));
                        
                         for (Player p : Bukkit.getServer().getOnlinePlayers()) {
                                 if (p.getInventory().getHelmet() != null && p.getInventory().getHelmet().getType() == Material.LEATHER_HELMET) {
                                         p.getInventory().setHelmet(getColorArmor(Material.LEATHER_HELMET, c));
                                 }
                                
                                 if (p.getInventory().getChestplate() != null && p.getInventory().getChestplate().getType() == Material.LEATHER_CHESTPLATE) {
                                         p.getInventory().setChestplate(getColorArmor(Material.LEATHER_CHESTPLATE, c));
                                 }
                                
                                 if (p.getInventory().getLeggings() != null && p.getInventory().getLeggings().getType() == Material.LEATHER_LEGGINGS) {
                                         p.getInventory().setLeggings(getColorArmor(Material.LEATHER_LEGGINGS, c));
                                 }
                                
                                 if (p.getInventory().getBoots() != null && p.getInventory().getBoots().getType() == Material.LEATHER_BOOTS) {
                                         p.getInventory().setBoots(getColorArmor(Material.LEATHER_BOOTS, c));
                                 }
                         }
                 }
         }, 0, 1);
 }

 private ItemStack getColorArmor(Material m, Color c) {
         ItemStack i = new ItemStack(m, 1);
         LeatherArmorMeta meta = (LeatherArmorMeta) i.getItemMeta();
         meta.setColor(c);
         i.setItemMeta(meta);
         return i;
 }
}