Sure you can call set(0), if you want, but a different method will be called. All constant integers automatically have int type. However, if you want to use the constant as a byte instead, you have to cast it. So set(0) will call the set() method that takes an int parameter, but set((byte)0) will call the set() method that takes a byte argument.
Personally, I think this is a poor programming practice since these two methods seem to be for different purposes and not at all related. It would be much more clear if set(byte clr) were setColor(byte clr) instead. Likewise, set(int a) should be setCoords(int a). Using names to clarify code is always a good thing.