I'm aware that at the moment Airbus offers two "sky" colours for their PFD; dark and light blue, and three "land" colours; green, red, and brown.

A couple of questions:

1) At what point is the colour selected? By the pilot in the cockpit, by a mechanic, or by the airline when it's ordered?

2) What's the "standard" colour combo?

3) Why is such an option available?