Added an example item whose variants use the same textures but different colours for the layers.

src/main/java/WayofTime/bloodmagic/item/ItemEnumColour.java

@@ -0,0 +1,67 @@
+package WayofTime.bloodmagic.item;
+
+import WayofTime.bloodmagic.BloodMagic;
+import WayofTime.bloodmagic.client.IVariantProvider;
+import WayofTime.bloodmagic.item.types.ISubItem;
+import it.unimi.dsi.fastutil.ints.Int2ObjectMap;
+import net.minecraft.creativetab.CreativeTabs;
+import net.minecraft.item.Item;
+import net.minecraft.item.ItemStack;
+import net.minecraft.util.NonNullList;
+import net.minecraft.util.math.MathHelper;
+import net.minecraftforge.fml.relauncher.Side;
+import net.minecraftforge.fml.relauncher.SideOnly;
+
+public class ItemEnumColour<T extends Enum<T> & ISubItem> extends Item
+{
+    //Copy of @ItemEnum, except all variants use the same textures with different colouring
+    protected final T[] types;
+
+    public ItemEnumColour(Class<T> enumClass, String baseName)
+    {
+        super();
+
+        this.types = enumClass.getEnumConstants();
+
+        setUnlocalizedName(BloodMagic.MODID + "." + baseName);
+        setHasSubtypes(types.length > 1);
+        setCreativeTab(BloodMagic.TAB_BM);
+    }
+
+    @Override
+    public String getUnlocalizedName(ItemStack stack)
+    {
+        return super.getUnlocalizedName(stack) + "." + getItemType(stack).getInternalName();
+    }
+
+    @Override
+    @SideOnly(Side.CLIENT)
+    public void getSubItems(CreativeTabs tab, NonNullList<ItemStack> subItems)
+    {
+        if (!isInCreativeTab(tab))
+            return;
+
+        for (T type : types)
+            subItems.add(new ItemStack(this, 1, type.ordinal()));
+    }
+
+    public T getItemType(ItemStack stack)
+    {
+        return types[MathHelper.clamp(stack.getItemDamage(), 0, types.length)];
+    }
+
+    public static class Variant<T extends Enum<T> & ISubItem> extends ItemEnum<T> implements IVariantProvider
+    {
+
+        public Variant(Class<T> enumClass, String baseName)
+        {
+            super(enumClass, baseName);
+        }
+
+        @Override
+        public void gatherVariants(Int2ObjectMap<String> variants)
+        {
+            variants.put(0, "type=normal");
+        }
+    }
+}

src/main/java/WayofTime/bloodmagic/item/types/AlchemicTypes.java

@@ -0,0 +1,59 @@
+package WayofTime.bloodmagic.item.types;
+
+import WayofTime.bloodmagic.core.RegistrarBloodMagicItems;
+import net.minecraft.item.ItemStack;
+
+import javax.annotation.Nonnull;
+import java.util.Locale;
+
+public enum AlchemicTypes implements ISubItem
+{
+    BASE(0x2e35ff);
+
+    final int potionColour;
+
+    AlchemicTypes(int colour1)
+    {
+        potionColour = colour1;
+    }
+
+    @Nonnull
+    @Override
+    public String getInternalName()
+    {
+        return name().toLowerCase(Locale.ROOT);
+    }
+
+    @Nonnull
+    @Override
+    public ItemStack getStack()
+    {
+        return getStack(1);
+    }
+
+    @Nonnull
+    @Override
+    public ItemStack getStack(int count)
+    {
+        return new ItemStack(RegistrarBloodMagicItems.ALCHEMIC_VIAL, count, ordinal());
+    }
+
+    public int getColourForLayer(int layer)
+    {
+        if (layer == 0)
+        {
+            return potionColour;
+        }
+        return -1;
+    }
+
+    public static int getColourForLayer(int variant, int layer)
+    {
+        if (variant >= AlchemicTypes.values().length)
+        {
+            return -1;
+        }
+
+        return AlchemicTypes.values()[variant].getColourForLayer(layer);
+    }
+}