public class ColorBlockEntity extends BlockEntity {
  public int color = 0x3495eb;
  
  public ColorBlockEntity(BlockPos pos, BlockState state) {
    super(TutorialBlockEntityTypes.COLOR_BLOCK, pos, state);
  }
  
  // The following two methods specify serialization of color data.

  @Override
  protected void readNbt(NbtCompound nbt, RegistryWrapper.WrapperLookup registryLookup) {
    super.readNbt(nbt, registryLookup);
    color = nbt.getInt("color");
    
    // When the data is modified through "/data" command,
    // or placed by an item with "block_entity_data" component,
    // the render color will be updated.
    if (world != null) {
      world.updateListeners(pos, getCachedState(), getCachedState(), 0);
    }
  }

  @Override
  protected void writeNbt(NbtCompound nbt, RegistryWrapper.WrapperLookup registryLookup) {
    super.writeNbt(nbt, registryLookup);
    nbt.putInt("color", color);
  }

  @Nullable
  @Override
  public Packet<ClientPlayPacketListener> toUpdatePacket() {
    return BlockEntityUpdateS2CPacket.create(this);
  }

  @Override
  public NbtCompound toInitialChunkDataNbt(RegistryWrapper.WrapperLookup registryLookup) {
    return createNbt(registryLookup);
  }

  @Override
  public @Nullable Object getRenderData() {
    // this is the method from `RenderDataBlockEntity` class.
    return color;
  }
}