When the Department of Homeland Security (search) raised its color-coded terror alert system on Sunday, everyone knew that it meant federal officials had learned new information about the threat of terrorism.

"It's disturbing, but I guess kind of anticipated," said Joe Saydlowski, 51, of Milford, Conn. "I think it provides more safety. I'm not sure how much additional protection there is in reality."

"It's just the government making everyone aware so if something happens, they can say, 'See, we told you,'" said Eric Kerzner, 29, a Milford commuter to New York City. "You can't be scared."

But for many U.S. residents, knowledge of the heightened security alert and appreciation of the effort Washington is making to alert the nation to potential risks is not matched by understanding of the color code's meanings.

"I usually pay attention," said Virginia jewelry salesman Al Waiss. "If it's code orange, that's one step above green, right?"

Waiss' colleagues at the Jewelry Express in Arlington jump in. "Orange is better than the yellow, no?" questioned Didi Montes de Oca.

"I always pay attention, but personally, I get confused," said Raul Fernandez. "Maybe they should do it like the traffic lights — red, yellow and green."

The Homeland Security Department raised its five-level alert system from its middle color yellow — "elevated" — to orange — "high" — in the wake of an increase in the number of intelligence reports suggesting the Al Qaeda terror network is trying to hit the United States again, possibly during the holidays.

The orange, or second-highest level — red at the top of the chart means the threat of an attack is "severe" — alerts federal departments and agencies to step up protective measures, including coordinating, state and local law enforcement, National Guard or other appropriate armed forces organizations; taking additional precautions at public events; preparing to execute contingency procedures and restricting access to facilities believed to be possible targets.

George Pinckney, public affairs officer for the city of Alexandria, Va., said the color coding system is "pretty clear" to local officials, and police and fire departments in his city are encouraged to stay mindful of what is going on in the community.

"It serves as a national guide and we follow suit in reminding employees of what steps the city can take in encouraging awareness.  [The alerts] remind us to be more vigilant. We always like to feel that we are vigilant at all times," he said.

But Homeland Security's use of the color code is just one of several indices designed to send a message to residents. And that's the crux of what's wrong with the system, say critics. With so many color codes competing for attention, the right message is frequently lost in a rainbow of warnings.

Furthermore, they add, placing too much emphasis on the color rather than the meaning behind it leaves people confused, causing them to tune out all together.

"To the extent that color coding is positive, it's self-defeating when you have different organizations using it for different purposes," said Chuck Hersey, manager of environmental programs for the Southeast Michigan Council of Governments (search), which has a color-coded index for its 10-year-old Ozone Action Program (search).

When the idea first arose to institute a color-coding system for ozone alerts, Hersey resisted it, to no avail. Now many localities are using them, and in many cases, the same color means different things, depending on the municipality, region or national index used or the type of alert. "I personally think it sends mixed messages," Hersey said.

On the national level, red means severe threat of terror attacks, according to the Homeland Security Department. But the Environmental Protection Agency also sends out an air quality alert in which red signals asthma sufferers to stay out of urban and industrial areas. In a metropolitan area, a red day could also mean soot levels are unhealthy, though not as unhealthy as purple.

Like the red alert, the Homeland Security Department's lowest two warning colors, blue and green, have not been used since the system was put into place. But doctors, who are frequently among the first responders in a terror attack, also recognize “code blue” as the highest emergency for their patients, and are trained to react accordingly.

Schools districts use color-coded systems as well. Montgomery County, Md., school officials order a "code red" when buildings go into emergency lockdowns. But in the nearby District of Columbia, red means students and teachers have the day off due to inclement weather.

In the Denver, Colo., area, red means residents can't burn their leaves outside, said Sherry Patten, communications director for the Denver Regional Council of Governments (search). The leaf-burning system does not cause as much consternation, however, since, the region only posts two colors for its leaf-burning rules — red and blue — the latter indicating that the air outside is fine for burning leaves.

"In our area, it's been around so long that people know it," Patten said, acknowledging that the same can't be said for new systems, which seem to be piling on.

"We just keep adding more. You need to accompany these color alerts with an explanation of what it is," and that's not always happening, Patten added.

At the time the government introduced the terror color code, shortly after the new Cabinet-level department was established in March 2002, Homeland Security Secretary Tom Ridge (search) said the index would be used "to measure and evaluate terrorist threats and communicate them to the public in a timely manner."

The grid "provides clear, easy to understand factors, which help measure threat," Ridge added.

Later, the homeland security chief acknowledged that the alerts could cause some confusion. But Pinckney said use of the alert system has cleared up many of the original problems.

"As we have had more alerts, people are becoming more aware in understanding what they are," Pinckney said.

Any failure is not with the grid, added Tom Grein, retired editor and publisher of The Observer Newspapers in Northern Virginia, but with the media's inability to help the public better understand the Homeland Security color code system.

"What does orange mean anyway -- that I should go out and buy a gun?" Grein asked. "Why not one through five, with five being the worst?"

He added that since the Sept. 11, 2001, terror attacks, people have been left confused and unsettled, and quick-hit messages regarding their safety do not help lessen those feelings.

"We try to put everything in its lowest common denominator form," Grein said. "We are used to sound bites. We're used to putting everything into one or two words instead of explaining it to anybody."

At least one county is hesitant to slide down the rainbow. According to Guillermo Cole, public information officer for the Allegheny Health Department in Pittsburgh, Pa., the color-code index has been ruled out so far for the county's new soot alert system.

"One of the concerns is we would be creating confusion, with all of these indices indicating one thing or another," Cole said. " I don't think the color is as important as the air quality description. That's what's really important, the advisory itself."

Fox News' Peter Brownfeld and the Associated Press contributed to this report.