A campaign ban on green clothing during the candidate's visits to Israel and Jordan has created wide puzzlement among observers of the Middle East.
In a memo to reporters, described as "a few guidelines we sent staff before departure to the Middle East," Obama advance staffer Peter Newell laid out rules on attire for Jordan and Israel.
First among them: "Do not wear green."
An Obama aide explained to reporters that green is the color associated with the militant Palestinian group Hamas. But while the color does appear on Hamas banners, there is no particular symbolism to wearing green clothes, experts said.
Moreover, green is more generally seen as a symbol of Islam.
"A ban on wearing green seems bizarre," said Richard Bulliet, a professor of Middle Eastern history at Columbia University, who said the color is associated with the family of the Prophet Mohammed.
"I would hazard the guess that the campaign's concern is more with distorted-and religiously inaccurate-reporting by Obama's detractors than with any actual signal that might be conveyed," he said, referring to false rumors that Obama is a Muslim. "You don't want to have some blogger come along and say 'Obama is showing his true color.'"
"I think they're just being overcautious to a ridiculous degree," Bulliet said.
Mohamad Bazzi, a professor of journalism at New York University and former Middle East bureau chief for Newsday, called the instruction "very strange."
"I guess green is the 'Hamas color' - but it's also the color of Islam!" Bazzi said in an email from Beirut. "That's one way for the Obama campaign to alienate 1.4 billion Muslims worldwide."
Though the campaign's other sartorial instructions - directing women to dress demurely - are fairly standard, Bazzi said he'd never heard it suggested before that journalists not wear green while traveling in the Middle East, an observation echoed by other reporters.
"I've been to the Middle East with Secretaries of State and on my own, and I've never heard of anything like that," said New York Sun national security reporter Eli Lake.
Obama's trip was organized independently of the State Department, and Secretary of State Condoleezza Rice advised American embassies Thursday to avoid helping presidential campaigns with their foreign trips.
Hamas, the group that controls the Gaza Strip, flies a green flag, as do some other Islamist groups. But the color appears on a vast array of official symbols, including the Saudi flag. Jordan's Queen Rania al-Abdullah has been pictured in green outfits.
Early images from Obama's trip also suggested that the rule is being observed in the breech: One cameraman on the tarmac in Amman can be seen in a green checked shirt.
"We wanted to be as respectful as possible. We wanted to go to the highest level," said Jen Psaki, an Obama spokeswoman in Amman, of the campaign's full list of sartorial suggestions, which also include a ban on nail polish and tank tops for women.
Another Obama spokesman, Bill Burton, didn't explain the admonition against wearing green, but downplayed the memo.
"It was an informal document put together by people on the ground compiling info from a range of sources," he said. "Some reporters on our trip had asked for advice on what to wear and so it was given to travelling press."
A spokesman for the Council on American Islamic Relations, Ibrahim Hooper, said Muslims might take offense at the campaign's instruction.
"Are you kidding?" Hooper asked, when told of the memo, calling the move a "misstep."
"The color green is associated with Islam worldwide," he said. &ldqu;Whether in some particularly tiny geographic location there's some other local association based on politics is one thing, but to ask people not to wear green - are they going to ask people if he goes to Ireland, are they going to ask them not to wear green or orange?"
The president of the Arab American Institute, James Zogby, said he didn't think the rule would give offense, but that he did find it puzzling.
"I've never heard of that before," he said, adding that nobody had ever suggested avoiding the color on his satellite television show, which airs weekly in the Arab world.
"This is an overreach on somebody's part," he said. "It's not going to insult anybody, nor is it going to offend them if somebody does wear green."
Officials at pro-Israel groups that lead groups of journalists to the region declined to comment, but people familiar with trips led by everyone from the American Israel Education Foundation (the charitable arm of the pro-Israel lobby AIPAC) to the White House and State Department to the Israeli government said they'd never heard of such a rule.
"Our folks in Jerusalem and the USA have no idea what this is about," said an official of one major American Jewish organization. "We have not ever suggested that people not wear the color green. During the disengagement from Gaza, the color orange was the color of the anti-disengagement folks, so we did advise folks not to make an unintentional political statement by wearing orange."
Jeff Ballabon, a Republican consultant active in pro-Israel causes, was also baffled by the explanation of the link between green and Hamas. "Why didn't he also ban the use of yellow, which is Hezbollah's color?"
"I hear they aren't going to order croissants because they're crescent-shaped," he quipped.
Budoff Brown reported from Amman; Smith from New York.
By Ben Smith and Carrie Budoff Brown