I have been using a basic buttercream icing recipie that taste amazing.  My only complaint is that when I color the icing and ice/smooth a cake, a day later the icing appears to have cracks. I have increased the amount of water I use in the icing but I still get the same results.  Any suggestions of how I can prevent it from drying out on the cake?

AMaybe lessen the water so its not so dry and keeps some moisture

I use milk (sometimes cream) instead of water and maybe your butter might not be enough.