官方發給你的身分與證明
這兩個都是你收著的文件：一張說你可以留下來，一張說你的保險在國外還算數。
noun · B1
An official US document that lets a person who is not a US citizen live and work in the United States permanently. Its formal name is the Permanent Resident Card.
綠卡
核心畫面
Picture a green card held out by someone in charge — an official at a desk, an insurer, an umpire on the pitch. The card itself does nothing; it is the green piece of paper that stands in for a decision already made about you. You may stay. You are covered. You have been warned once. In each case the colour is the label, and the card is the short way of saying the whole sentence.
可以想成一張綠色的卡被某個有權力的人遞出來或舉起來：櫃檯後的官員、保險公司、球場上的裁判。卡片本身什麼也不做，它只是…更多收起
可以想成一張綠色的卡被某個有權力的人遞出來或舉起來：櫃檯後的官員、保險公司、球場上的裁判。卡片本身什麼也不做，它只是代表一個已經做好的決定。你可以留下來。你的保險有效。你已經被提醒過一次了。三種情況裡，綠色都只是那張卡的標籤，而卡片是把一整句話濃縮成一個可以拿在手上的東西。至於為什麼是綠的，多半是當年印出來就長那樣，後來顏色換了，名字還是留著。From the word’s history
Wiktionary records that the US work permit is named from the historical greenish colour of the card, first used in 1946, and that the American Express charge card of the same name came from its green design made to resemble US dollar bills.
Wiktionary 記載：美國那張工作證件的名字來自卡片早年的綠色，最早在 1946 年使用；而同名的美國運通簽帳卡則是因為卡面設計成類似美元的綠色。也就是說，這些用法的共同點不是同一個來源，而是同一個做法——用顏色替一張卡命名。
Wiktionary (kaikki extract) entry 'green card', etymology_text supplied in this packet; source_ref kaikki:3f6f69a190036ae4:1385241552
Two branches
場上舉起來的那張牌
這一支不是你收著的證件，而是裁判舉起來給大家看的訊號；相同的只有「顏色代表一個決定」這個做法。
noun · B2
In field hockey, a card that the umpire shows to a player as a first warning after they break a rule. If the player offends again, a yellow card or a red card may follow.
綠牌（曲棍球警告）