ItemColors implementation

blockstates_testOre.json

{
  "variants": {
    "normal": { "model": "examplemod:testOre" }
  }
}

ClientProxy.java

package com.example.examplemod;

import net.minecraft.client.Minecraft;
import net.minecraft.client.renderer.block.model.ModelResourceLocation;
import net.minecraft.item.Item;
import net.minecraftforge.client.model.ModelLoader;
import net.minecraftforge.fml.common.FMLLog;

/**
 * Created by sbarbour on 4/7/16.
 */
public class ClientProxy extends CommonProxy {

	private ModelResourceLocation testItemRL = new ModelResourceLocation("examplemod:testItem", "inventory");
	private ModelResourceLocation testOreRL = new ModelResourceLocation("examplemod:testOre", "inventory");

	@Override
	public void registerRenderers() {
		FMLLog.info("Client-side");
		Minecraft.getMinecraft().getRenderItem().getItemModelMesher().register(ExampleMod.testItem, 0, testItemRL);
		Minecraft.getMinecraft().getRenderItem().getItemModelMesher().register(ExampleMod.testItem, 1, testItemRL);
		Minecraft.getMinecraft().getItemColors().registerItemColorHandler(new TestItem.ColorHandler(), ExampleMod.testItem);

		Minecraft.getMinecraft().getRenderItem().getItemModelMesher().register(Item.getItemFromBlock(ExampleMod.testOre), 0, testOreRL);
		Minecraft.getMinecraft().getBlockColors().registerBlockColorHandler(new TestOre.ColorHandler(), ExampleMod.testOre);
		Minecraft.getMinecraft().getItemColors().registerItemColorHandler(new TestOre.ColorHandler(), ExampleMod.testOre);
	}

	@Override
	public void loadModels() {
		ModelLoader.setCustomModelResourceLocation(ExampleMod.testOreItem, 0, testOreRL);
	}

}

CommonProxy.java

package com.example.examplemod;

import net.minecraftforge.fml.common.FMLLog;

/**
 * Created by sbarbour on 4/7/16.
 */
public class CommonProxy {

	public void registerRenderers(){
		FMLLog.info("Server-side");
	}

	public void loadModels() {
	}
}

ExampleMod.java

package com.example.examplemod;

import net.minecraft.block.Block;
import net.minecraft.init.Blocks;
import net.minecraft.item.Item;
import net.minecraftforge.fml.common.FMLLog;
import net.minecraftforge.fml.common.Mod;
import net.minecraftforge.fml.common.Mod.EventHandler;
import net.minecraftforge.fml.common.SidedProxy;
import net.minecraftforge.fml.common.event.FMLInitializationEvent;
import net.minecraftforge.fml.common.event.FMLPostInitializationEvent;
import net.minecraftforge.fml.common.event.FMLPreInitializationEvent;
import net.minecraftforge.fml.common.registry.GameRegistry;

@Mod(modid = ExampleMod.MODID, version = ExampleMod.VERSION)
public class ExampleMod
{
    public static final String MODID = "examplemod";
    public static final String VERSION = "1.0";

    @SidedProxy(clientSide = "com.example.examplemod.ClientProxy", serverSide = "com.example.examplemod.CommonProxy")
    public static CommonProxy proxy;

    public static Item testItem = new TestItem("testItem");
	public static Block testOre = new TestOre("testOre");
	public static Item testOreItem = new TestOreItem(testOre);

    @EventHandler
    public void preInit(FMLPreInitializationEvent event) {
        GameRegistry.register(testItem);
	    GameRegistry.register(testOreItem);
	    GameRegistry.register(testOre);
	    proxy.loadModels();
    }

	@EventHandler
	public void postInit(FMLPostInitializationEvent event) {
		FMLLog.bigWarning("Post-init");
		proxy.registerRenderers();
	}
}

models_block_testOre.json

{   "parent": "block/block",
  "elements": [
    {   "from": [ 0, 0, 0 ],
      "to": [ 16, 16, 16 ],
      "faces": {
        "down":  { "uv": [ 0, 0, 16, 16 ], "texture": "#base", "tintindex": 0, "cullface": "down" },
        "up":    { "uv": [ 0, 0, 16, 16 ], "texture": "#base", "tintindex": 0, "cullface": "up" },
        "north": { "uv": [ 0, 0, 16, 16 ], "texture": "#base", "tintindex": 0, "cullface": "north" },
        "south": { "uv": [ 0, 0, 16, 16 ], "texture": "#base", "tintindex": 0, "cullface": "south" },
        "west":  { "uv": [ 0, 0, 16, 16 ], "texture": "#base", "tintindex": 0, "cullface": "west" },
        "east":  { "uv": [ 0, 0, 16, 16 ], "texture": "#base", "tintindex": 0, "cullface": "east" }
      }
    },
    {   "from": [ 0, 0, 0 ],
      "to": [ 16, 16, 16 ],
      "faces": {
        "down":  { "uv": [ 0, 0, 16, 16 ], "texture": "#overlay", "tintindex": 1, "cullface": "down" },
        "up":    { "uv": [ 0, 0, 16, 16 ], "texture": "#overlay", "tintindex": 1, "cullface": "up" },
        "north": { "uv": [ 0, 0, 16, 16 ], "texture": "#overlay", "tintindex": 1, "cullface": "north" },
        "south": { "uv": [ 0, 0, 16, 16 ], "texture": "#overlay", "tintindex": 1, "cullface": "south" },
        "west":  { "uv": [ 0, 0, 16, 16 ], "texture": "#overlay", "tintindex": 1, "cullface": "west" },
        "east":  { "uv": [ 0, 0, 16, 16 ], "texture": "#overlay", "tintindex": 1, "cullface": "east" }
      }
    }
  ],
  "textures": {
    "particle": "blocks/stone",
    "base": "blocks/stone",
    "overlay": "examplemod:blocks/oreFlecks"
  }
}

models_item_testItem.json

{
  "parent": "item/generated",
  "textures": {
    "layer0": "examplemod:items/testItem_layer0",
    "layer1": "examplemod:items/testItem_layer1",
    "layer2": "examplemod:items/testItem_layer2"
  }
}

models_item_testOre.json

{
  "parent": "examplemod:block/testOre",
  "display": {
    "thirdperson": {
      "rotation": [ 10, -45, 170 ],
      "translation": [ 0, 1.5, -2.75 ],
      "scale": [ 0.375, 0.375, 0.375 ]
    }
  }
}

TestItem.java

package com.example.examplemod;

import net.minecraft.client.renderer.color.IItemColor;
import net.minecraft.creativetab.CreativeTabs;
import net.minecraft.item.Item;
import net.minecraft.item.ItemStack;
import net.minecraftforge.fml.relauncher.Side;
import net.minecraftforge.fml.relauncher.SideOnly;

import java.awt.*;
import java.util.List;

public class TestItem extends Item {
	public TestItem(String unlocalizedName) {
		super();

		this.setUnlocalizedName(unlocalizedName);
		this.setCreativeTab(CreativeTabs.tabMisc);
		this.setHasSubtypes(true);
		this.setRegistryName("examplemod","testItem");
	}

	@Override
	@SideOnly(Side.CLIENT)
	public void getSubItems(Item itemIn, CreativeTabs tab, List<ItemStack> subItems)
	{
		for (int i = 0; i < 2; i++)
		{
			subItems.add(new ItemStack(this, 1, i));
		}
	}

	public static class ColorHandler implements IItemColor {
		@Override
		public int getColorFromItemstack(ItemStack stack, int tintIndex) {
			switch(stack.getMetadata()) {
				case 0:
					switch(tintIndex) {
						case 0:
							return -1;
						case 1:
							return Color.BLUE.getRGB();
						case 2:
							return Color.RED.getRGB();
					}
				case 1:
					switch(tintIndex) {
						case 0:
							return -1;
						case 1:
							return Color.CYAN.getRGB();
						case 2:
							return Color.YELLOW.getRGB();
					}
			}
			return -1;
		}
	}
}

TestOre.java

package com.example.examplemod;

import net.minecraft.block.Block;
import net.minecraft.block.material.Material;
import net.minecraft.block.state.IBlockState;
import net.minecraft.client.renderer.color.IBlockColor;
import net.minecraft.client.renderer.color.IItemColor;
import net.minecraft.creativetab.CreativeTabs;
import net.minecraft.item.ItemStack;
import net.minecraft.util.BlockRenderLayer;
import net.minecraft.util.math.BlockPos;
import net.minecraft.world.IBlockAccess;
import net.minecraftforge.fml.common.FMLLog;
import net.minecraftforge.fml.relauncher.Side;
import net.minecraftforge.fml.relauncher.SideOnly;

import java.awt.*;

public class TestOre extends Block {
	public TestOre(String unlocalizedName) {
		super(Material.rock, Material.rock.getMaterialMapColor());
		this.setRegistryName("examplemod",unlocalizedName);
		this.setUnlocalizedName(unlocalizedName);
		this.setCreativeTab(CreativeTabs.tabBlock);
	}

	@SideOnly(Side.CLIENT)
	public BlockRenderLayer getBlockLayer()	{
		return BlockRenderLayer.CUTOUT_MIPPED;
	}


	public static class ColorHandler implements IBlockColor, IItemColor {
		@Override
		public int colorMultiplier(IBlockState state, IBlockAccess p_186720_2_, BlockPos pos, int tintIndex) {
			int color = (tintIndex == 0 ? -1 : Color.CYAN.getRGB());
			FMLLog.info("tintIndex: " + tintIndex + " - " + color);
			return color;
		}

		@Override
		public int getColorFromItemstack(ItemStack stack, int tintIndex) {
			return (tintIndex == 0 ? -1 : Color.CYAN.getRGB());
		}
	}
}

TestOreItem.java

package com.example.examplemod;

import net.minecraft.block.Block;
import net.minecraft.item.ItemBlock;

/**
 * Created by sbarbour on 4/8/16.
 */
public class TestOreItem extends ItemBlock {

	public TestOreItem(Block block) {
		super(block);
		setRegistryName("examplemod",block.getUnlocalizedName());
		setUnlocalizedName(block.getUnlocalizedName());
	}
}

Thanks, this helped me a bit to learn how to implement it my own way.
If you're interested, you can see how I did here.

Some suggestions: _I believe it would be a better practice to use ModelLoader#setCustomModelResourceLocation to register model file locations. Also, you should register your colour handlers in the initialization not post-initialization phase.