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; Carrot Wine. Anchorage Brewing Dregs Cider
Secondary: Rhubarb Wine, House Cider
Tertiary (or higher):
Drinking: House Cider, Cherry Cyser, Belgian Walnut Graff, Rhubarb Wine