Making very red icing is quite difficult, it is quite important to use very good quality gel food colouring because liquid colouring makes your icing too runny. Also, if you're using butter cream icing, it helps to use white food colouring first to make the yellow icing white before turning it red otherwise you end up with peach instead.
When it comes to making black icing, the easiest way to obtain a true black without turning it bitter (which happens when adding too much food colouring) is to first add cocoa to your icing and make it chocolate. Once your icing is dark brown, add your black food colouring and it will quickly turn black.
I also used an extra cake mix to make a batch of cupcakes and decorated them like mini ladybirds so that we had enough cake to go around.
Give it a try, it is quite an easy cake, I had very little baking experience and found it not too challenging!