These are the cake icing laws, right? 
 
red velvet or carrot cake = cream cheese icing
 
yellow cake = choc buttercream recipe from the back of Hershey’s cocoa.  I did make a caramel frosting to go with a scratch yellow cake which was good, and I’d make again (the cake recipe didn’t have much taste and was too dry and crumbly
 
chocolate cake =  depends on the recipe, if it’s my grandmother’s choc sheet cake I make the chocolate icing that goes with it, otherwise, vanilla buttercream from the back of the confectioner’s sugar box