Very nice! Now my stem blocks work well with custom colors rendered by using this.
@SubscribeEvent
public void registerBlockColors(final ColorHandlerEvent.Block event) {
event.getBlockColors().register(myBlockColor, coloredBlock1, coloredBlock2, ...);
}
Although it's growth_age0 ~ growth_age7 renders the same color which I defined,but that's enough for me.Thank you @warjort much much😀.