Good Riddles

Question: What goes black when you buy it, red when you use it, and goes white when you throw it away?

Question: There are five people at a table and a pie sliced into 5 pieces. Each person has a piece of pie in front of them, yet the pie tin still has a piece of pie in it. How is this possible?

Question: I'll bring out your bulls,
and slow your roll.
I may even come out of your skull.

What am I?

Question: Connect all 9 of the dots using 4 straight lines or less. Do so without lifting the pen or tracing the same line more than once.

Question: What building has the most stories?