When using the command on an item that also shows the hand holding it, the hand is colored but the item is not. Ignore the error in the chat, that was from trying an invalid color code.

I can't tint custom renders like that. So i can't fix this.

I thought that might be the case. What's the command or color code to revert to default, if there is one?

Setting the tint to white should turn it back to normal.