Blue

Question 1

depression caused by lack of sunshine

Answer 1

winter blues

Question 2

to appear out of nowhere

Answer 2

bolt from the blue

Question 3

to be very blue

Answer 3

postcard-blue

Question 4

to make a huge but vain effort to win an argument

Answer 4

to argue until you are blue in the face

Question 5

a true conservative

Answer 5

a true blue

Question 6

to censor

Answer 6

to blue pencil