Where did all the celebrities go?

The red ribbons gave way to the pink ribbons, which were overtaken by the yellow wristbands -- until light blue ribbons came along. And they’ve all been shoved aside by the latest color to wash over Hollywood: green.

Maybe it’s the burnout factor. Or perhaps it’s because Hollywood has a short attention span. But as AIDS enters its 25th year, it is no longer The Cause among celebrities. There is also the perception that AIDS now affects only developing nations instead of the U.S., where ever-improving medical cocktails are helping those with HIV live longer.

Whatever the reason, the issue that once galvanized Hollywood is sharing the spotlight with a long list of causes: There’s breast cancer, testicular cancer and African debt relief. There’s Sept. 11, Katrina, the tsunami and the humanitarian crisis in Darfur, Sudan. And, most recently, global warming.

Angelina Jolie is bringing attention to the plight of orphans in Africa, in the latest round donating the proceeds of the sale of photos of newborn daughter Shiloh to African children’s charities. Leonardo DiCaprio, who is involved in a range of environmental issues, has his own eco-website. Ted Danson is fighting to clean up the oceans. And just Tuesday, sheriff’s deputies evicted actress Daryl Hannah from a tree in South Central community gardens in Los Angeles, where she was protesting the impending demise of one of the largest urban farms in the country.

There are so many rallying calls that some stars have completely given up wearing any symbol for fear of offending one group or another. During her acceptance speech after winning an MTV award recently, actress Jessica Alba was judicious: “Practice safe sex and drive hybrids if you can.”

Local AIDS groups, struggling to raise funds, are longing for the days when they were the central focus of the entertainment industry’s activism.

“There are a lot more demands and requests from great causes for people’s time and energy,” said Craig Thompson, executive director of AIDS Project Los Angeles. “Frankly, for celebrities it’s become a bit of a political conundrum.”

To be sure, there are a number of young stars taking up the AIDS issue, focusing their efforts on raising awareness in Africa, where the disease is crushing. (Worldwide, 25 million people have died of AIDS since 1981, and 2.8 million will die this year, according to the World Health Organization. Comparatively, more than half a million people in the U.S. have died of the disease over the last 25 years).

In May, actress Naomi Watts announced that she was joining the international fight after taking a trip to Zambia, where only 1 in 5 people stricken with AIDS receives treatment. “Given these stark realities, I could no longer stand on the sidelines,” she told reporters at a news conference at the United Nations in New York.

“You can’t underestimate what Hollywood has done for the issue and will continue to do for the issue,” gay activist and celebrity publicist Howard Bragman said. “We’ve lost too many people to forget.”

But he added: “There is the burnout factor.”

Thompson said AIDS Project Los Angeles -- with an ever-expanding caseload of HIV patients -- has fought over the last few years to increase its budget by a mere 3%, barely enough to keep up with inflation. “It’s not easy getting people out to our events,” he said. Los Angeles’ Minority AIDS Project is also struggling. Once the beneficiary of tens of thousands of dollars in celebrity donations, the project, which serves mostly lower-income residents in South Los Angeles, considered closing its doors last year.

“In the beginning, there was a lot of support from Hollywood,” said Victor McKamie, the executive director of the project. “People were calling us asking what they could do to help. Now we can’t even get them to return our calls.”

A more obvious indicator of the flagging interest in AIDS in the entertainment industry is the absence of the once-omnipresent red ribbon, which not too long ago was a de rigueur Oscar accessory.

It’s been at least five years since AIDS Project Los Angeles was asked to hand them out at the award shows, Thompson said. “I’m not sure people over the last few years were even noticing them anymore.

“Now there’s a ribbon for everything and every color and every cause,” he said. There’s pink for breast cancer, yellow for testicular cancer, light blue for tsunami relief.

“If they wear a red ribbon, they have to turn down the ribbons of four other organizations,” he said of the dilemma faced by celebrities. “It just became too politically difficult to wear one at the expense of another. We’ve acknowledged that people have moved on.”

Bragman sees Hollywood’s diverted attention as a good thing. It shows that the urgency -- at least in this country -- is easing because people are living longer. “If there was more urgency,” he said, “there wouldn’t be any of us left.”

Actor Paul Michael Glaser, whose wife, Elizabeth, died of AIDS after contracting the disease through a blood transfusion, believes Hollywood reflects the views of the rest of the country.

“It’s kind of the nature of society,” he said. (His wife unknowingly passed the virus on to daughter Ariel in breast milk and to son Jake in utero. She founded the Elizabeth Glaser Pediatric AIDS Foundation after Ariel’s death.) “When the AIDS epidemic first became visible, it was the darling disease. Then it went off to breast cancer and other things.”

At the moment, one of the hottest issues in town is the environment -- and even AIDS activists agree that’s a cause that is hard to argue with. “AIDS isn’t going to matter if there’s not a world left,” said Bragman, who is also supporting the green movement.

Reflecting Hollywood’s interest in the environment, Vanity Fair recently came out with a “green” issue featuring George Clooney, Julia Roberts, former Vice President Al Gore and Robert F. Kennedy Jr. on the cover.

Gore has also energized stars with his doomsday documentary on global warming, “An Inconvenient Truth.” At the Los Angeles premiere several weeks ago, stars walked down a green carpet to meet a throng of reporters. Among those attending were Hannah, Alba and Sharon Stone, who stood in line after the movie to greet Gore and offer their support.

Several days later, Stone shifted her focus back to AIDS, traveling to the Cannes Film Festival, where the actress known for her dedication to the cause helped lead an event to raise funds for AIDS research.

And there are other stalwarts still at work: Elton John and Elizabeth Taylor remain two of Hollywood’s biggest fundraisers for AIDS efforts. Recently designer Kenneth Cole launched an ambitious ad campaign to reeducate Americans about the epidemic. The ads feature more than a dozen actors, including Tom Hanks and Will Smith, and singer Alicia Keys. They state plainly: “We all have AIDS.” Meanwhile, Adrien Brody’s face is on a YouthAIDS billboard on Highland Avenue calling for young people to address the issue.

The most powerful advocacy, however, is aimed at fighting the deadly disease -- along with a number of other crises -- in Third World countries. Bono announced earlier this year that he was starting project Red to raise funds in the global fight against AIDS, along with tuberculosis and malaria.

Last year, Jolie -- perhaps Hollywood’s most visible young activist -- went to Washington to meet with lawmakers. She succeeded in persuading politicians to sign the Assistance for Orphans and Other Vulnerable Children in Developing Countries Act, which mandates that the U.S. spend 10% of its global AIDS assistance budget to help children.

The father of Jolie’s newborn girl, Brad Pitt, was also in town doing some politicking. As an ambassador of advocacy group DATA (Debt, AIDS, Trade, Africa), he spent two days meeting with officials, including Sen. Tom Harkin (D-Iowa), to “gain a better understanding of the trade issues in Africa, AIDS and extreme poverty,” according to a DATA representative.

Thompson, of AIDS Project Los Angeles, said he admires the new generation of Hollywood celebrity activists who have stepped forward. “They’re doing this century what their predecessors did between 1981 and 1986, but on an international scale. I understand from a humanitarian aspect they’re doing a very good thing.”

But he added: “I am a little envious.”