A “red line” is a figurative point (this could be a country’s border; it is not an actual red line) where, if crossed, actions such as war could commence. Several world leaders have declared “red lines.”
 
A “pink line” (pink + red line) is a weak “red line”—a line that includes the white of surrender, making it pink (effeminate or weak). “The pink line: If Assad used chemical weapons, what will Obama do?” was printed in the Chicago (IL) Tribune in April 2013 about the situation in Syria. “Pink Line over Damascus: Obama has backed himself into a corner” was printed in May 2013, as was “Why Obama’s ‘red line’ in Syria has turned pink.” “Putin crosses Obama’s pink line” was written by conservative radio talk show host Michael Savage in March 2014, regarding the situation in Ukraine.
 
   
Wikipedia: Red line (phrase)
Red line (Hebrew: קו אדום‎, Kav Adom) is a phrase used in both English and Hebrew to mean a figurative point of no return or line in the sand, or “a limit past which safety can no longer be guaranteed.”
 
Origins
The origin of the phrase in English traces to a red-coated Scottish regiment at the Battle of Balaclava in the Crimean War, at an action known as The Thin Red Line. A journalist described a “thin red streak tipped with a line of steel” with the appearance of the 93rd (Highland) Regiment and parts of the Turkish army as they stood before (and repelled) a vastly superior force of Russian cavalry. This action was famously described by Rudyard Kipling in the poem Tommy as “the thin red line of ‘eroes [heroes].” The term “the thin red line” later referred to the Argyll and Sutherland Highlanders and their job to defend the Empire and the United Kingdom after the incorporation of the Argylls and Sutherlands into a single regiment now known as the Argyll and Sutherland battalion of the Royal Regiment of Scotland.
   
Twitter   
i ♥ humanity
‏@ixh
“The pink line” Obama’s hometown Chicago tribune mocks Syria’s red line warning, demands action from WH
@slaughteram http://my.chicagotribune.com/#section/-1/article/p2p-75623814/ …
10:26 PM - 24 Apr 2013
 
Chicago (IL) Tribune
The pink line
If Assad used chemical weapons, what will Obama do?
April 25, 2013
President Barack Obama drew a clear red line last August when he threatened direct military action if Syrian President Bashar Assad unleashed chemical or biological weapons against rebels seeking to topple him:
(...)
American officials note that it is difficult to corroborate information in a turbulent war zone where the U.S. reportedly has few spies on the ground. U.N. experts also have been barred by the Assad regime from entering Syria to investigate the chemical weapons charges.
 
In other words, the red line is still a shade of ... pink.
 
National Review Online
MAY 9, 2013 8:00 PM
Pink Line over Damascus
Obama has backed himself into a corner.
By Charles Krauthammer
You know you’re in trouble when you can’t even get your walk-back story straight. Stung by the worldwide derision that met President Obama’s fudging and fumbling of his chemical-weapons red line in Syria, the White House leaked to the New York Times that Obama’s initial statement had been unprepared, unscripted, and therefore unserious.
 
The next day Jay Carney said precisely the opposite: “Red line” was intended and deliberate.
   
RT.com
Why Obama’s ‘red line’ in Syria has turned pink
By Patrick Henningsen
Published time: May 14, 2013 16:07
(...)
The ‘Red Line’ was a historical first, in the sense that this ultimatum was woven to insure a case for intervention either way and would mean that the US would be free to attack the Assad government militarily even if the foreign terrorist confab were the guilty party. It was an attempt to essentially widen the definition of a case for intervention, essentially rewriting the language of international law and replacing it with language more suitable for a global police force who could act out under the guise of ‘keeping the peace’. An extraordinary first in global diplomacy for sure, and a very difficult line to enforce in view of an international community cannot see the sense in such an insane equation put forth by a US President.
 
Another reason for Obama’s fading ‘Pink Line’ in Syria is the Benghazi Hearings. Events of this week have finally begun to expose the inadequacy in US intelligence circles, as well as the institutional corruption that allows political gain to trump American lives in Washington.
   
The Wall Street Journal
WORD ON THE STREET
The Long History of the Phrase ‘Red Line’
By BEN ZIMMER
July 19, 2013 7:32 p.m. ET
(...)
But “red line” also has a long history in Israel as a foreign-policy metaphor. In 1975, Foreign Minister Yigal Allon said that Washington “has managed to draw a red line which all the Arab countries know they must not cross—that America is not going to sacrifice Israel for the sake of Arab support.” Then-prime minister Yitzhak Rabin used the phrase to refer to the line past which the Syrian army should not be allowed to cross after its 1976 occupation of Lebanon.
 
In English usage, the history of the expression can be traced back to the courageous stand by a red-coated Scottish regiment at the Battle of Balaclava in the Crimean War, immortalized by Rudyard Kipling as “the thin red line of ‘eroes.” James Jones used “The Thin Red Line” as the title of his 1962 novel about a World War II battle in which American troops similarly held the line.
   
Twitter
HETEROSEXUAL WOMAN ™
‏@tracieeeeee
Cuz OBAMA would say if you cross the pink line there will be consequences @M_McMullenAggie @SpreadButter
7:48 PM - 26 Feb 2014
   
WND
March 2, 2014
WARS AND RUMORS OF WARS
PUTIN CROSSES OBAMA’S PINK LINE
Exclusive: Michael Savage declares, ‘The neocons don’t care which side you’re on’
By Michael Savage
Let me make sense of what’s happening in Ukraine for you as that country descends into armed chaos, threatening to oust the legitimately elected Ukrainian President Viktor Yanukovich and place the country in the hands of rebel forces spearheaded by Ukrainian neo-Nazis and Chechen Islamist radicals.
 
Twitter
Squid’s Lighters
‏@squidslighters
Too bad we don’t still own the Panama Canal; Obama or Kerry could draw a pink line so Putin’s navy could easily find it. #TBYG
3:50 PM - 3 Mar 2014