Pink slip: Notice of termination of employment; a note from your employer telling you that you've lost your job. (USA)
P45: In the United Kindgom and Ireland, P45 is the reference code of a form titled Details of employee leaving work.

In the 1920's, large corporations developed color-coded paper communication systems. Pink paper was used to send the message "you're fired."
1) I think our boss enjoys handing out pink slips.
2) The factory is closing next week, and all 500 employees received pink slips today.
3) On June 27, 2007, the day of his resignation as Prime Minister, Tony Blair jokingly remarked during his final Prime Minister's Questions about receiving his P45: “I received the following communication by urgent letter yesterday: “Details of employee leaving work: Surname Blair. First name T”
4) "A hora do bilhete azul pode ser cor-de-rosa... Investe-se de forma a tornar o tão temido bilhete azul em algo menos traumático para o funcionário. "
Source: Knights English and Other