1- a grey area (British & Australian, American)

Exp. : a subject or problem that people do not know how to deal with because there are no clear rules.

Sentence: The election to happen is a bit of a grey area because people are confused about the number of the voters.

Turkish version: arap saçı(na dönmek)

2- grey matter (British & Australian, humorous, American, humorous)

Exp. : your intelligence.

Sentence: Arog and Gora are nice but they don't exactly stimulate the old grey matter.

Turkish version: -

3- the men in grey suits

Exp. : men in business or politics who have a lot of power and influence although the public does not see them or know about them.

Sentence: It is the men in grey suits who will decide what we'll see in politics.

Turkish version: -

4- to get/have gray hair from

Exp. : To be very worried or upset by. Similarly, give gray hair to means "to worry someone".

Sentence: I have got grey hair from the assignments. 

Turkish version: turşu gibi olmak, üstüne fenalık gelmek, 

5- the grey pound

Exp. : In the UK, the grey pound is an idiom used for the economic power of elderly people.

Sentence: My aunt spends her grey pound to travel around the world.

Turkish version: -

6- grey cells

Exp. : brain.

Sentence: Use your grey cells to understand the modern art but sometimes it is not enough.

Turkish version: -

7- to go grey

Exp. : become grey-haired.

Sentence: Since she is in her 40s, she is going grey.

Turkish version: saçların ağarması