The magnetic effects are not caused or determined by the colour of a magnet. The north pole could be dyed yellow or green while still being a north pole. Two whole magnets attract each other as well when their opposite poles come close to each other. The attraction between the pieces is not a proof for magnets with a single pole, so-called monopoles.

Magnets always have two poles. We talk about dipoles. This is explained by the model of elementary magnets. The magnetic effects can be traced back to the elementary magnets, which work on the inside. We can think of these as tiny magnets, which are dipoles themselves. They stay in the magnet even when it is broken into small pieces.