Shouldn't hurt anything--you'd have to add a redicolous amount to get any flavours from it.
You'd add the colouring just before bottling, maybe before racking the final time so it gets gently mixed in.
There is one secret ingredient that makes anything better......time.
Primary: House Cider; Rhubarb Wine (two batches), Carrot Wine, Malliard Botchet
Secondary: Mahlab Metheglin
Tertiary (or higher): Raspberry Cider
Drinking: House Cider, Rhubarb Saisoff