Rendering an Item in a Chest GUI

Hi I am trying to render a light green stained glass pane under an item in the first slot of a chest that I open. This was my attempt at it but I cannot get it to render the item can anyone help me. Also I would like this to be entirely client sided. Thank you in advance!

	@SubscribeEvent
	public void onGuiOpen(GuiOpenEvent event) {
		String currentGui;
		// Check type of gui
		if (event.gui instanceof GuiChest) {
			// Save current gui
			GuiChest chest = (GuiChest) event.gui;
			ContainerChest container = (ContainerChest) chest.inventorySlots;
			// Get name of current gui
			currentGui = container.getLowerChestInventory().getDisplayName().getUnformattedText();
			System.out.println(currentGui);
			// Create stained glass pane
			ItemStack stainedGlassPane = new ItemStack(Item.getItemFromBlock(Blocks.stained_glass_pane), 1, 5);
			Slot firstSlot = chest.inventorySlots.inventorySlots.get(0);
	        	int xPos = firstSlot.xDisplayPosition + (firstSlot.xDisplayPosition - 16) / 2; // Center horizontally
	        	int yPos = firstSlot.yDisplayPosition + (firstSlot.yDisplayPosition - 16) / 2; // Center vertically
			// Render the stained glass pane onto the GUI
			RenderHelper.enableGUIStandardItemLighting();
			Minecraft.getMinecraft().getRenderItem().renderItemAndEffectIntoGUI(stainedGlassPane, xPos, yPos);
			RenderHelper.disableStandardItemLighting();
		}
	}

Edit: Forgot to mention that I am using Forge 1.8.9 - 11.15.1.2318

Edited August 9, 20232 yr by chrisrca
Version