most hydrias are painted in a teqnique called black-figure
Whatever colour they happen to be painted (one can not see the siren usually). I hope you are not confusing the siren (which makes the noise) with the flashing lights (which are blue).
no
What colour should a basketball hoop be painted?
Whatever colour it has been painted. There is no single colour a hull has to be.
a hydria
Black
It is painted in more than one colour for camouflage purposes.
Look around the world and steam locomotives were painted in all sorts of colours and colour schemes. I think the predominate colour was actually black
black
The walls were painted an egg yellow.
because to prevent it from corrosion
It is the colour most visible in fog