go out in those Dame Edna glasses...that alien haircolor...those stripes! Okay, sometimes they do. When is telling the truth a favor and when should you just zip it? O’s beauty director, VALERIE MONROE, sorts it out.

It was my first (and come to think of it, last) time as a guest on the Oprah show. Put yourself in my place. Would you be nervous? Even if you knew Oprah a little and she had always been unfailingly kind and supportive? I’ll answer for you: Yes. You’d be tired, too, because the night before the show you’d have been up very late in your hotel room, lying in your unfamiliar bed, counting not sheep but the innumerable ways available for you to humiliate yourself. At some point, I must have received a wake-up call, because the next thing I knew I was wearing what seemed like a couple of bottles of foundation and squinting into very bright lights. Oprah introduced me as the beauty director of her magazine. And, could it be? Yes, it was true! I appeared to be a genius: People applauded every time I opened my mouth. (Sometimes, confusingly, even before I opened my mouth, but so what?) It was going swell until an audience member asked, “What should I say to a friend who has dyed her hair a wildly unattractive color?” I turned to Oprah and said that if she, for example, were to make an unfortunate choice, I would try to think of every kind thing I could say before I told her what I really thought. To my surprise—followed swiftly by my alarm— Oprah disagreed. A real friend, she said with great conviction, will always tell you the bald, unvarnished truth. That’s what a good friend does, she said; in fact, that’s what her best friend, Gayle King, does. About one particularly electrifying hairstyle, for example, Gayle remembers telling Oprah that she looked as if she’d stuck her finger in a socket. (Oprah remembers, too.)

But while this kind of honesty works for them, it’s shocking, unthinkable, to others—me, for instance, and I’m not alone. “I’m a total sissy when it comes to telling my friends something dicey about the way they look,” says Rachel Simmons, Rhodes scholar and author of Odd Girl Out, in which she examines the subject of girls and aggression. “I get nauseated just thinking about it.” The roots of her reluctance to criticize are deeper than simple queasiness about confrontation. “Women tend to take criticism very personally,” she says. “They often feel responsible for and ashamed of their mistakes. A lot of women see it as criticism not of a discrete choice they’ve made but of who they are as a person. So their feelings may spiral downward from ‘I made the wrong choice’ to ‘I’m a bad person’ to ‘No one will love me.’”

With the stakes that high, you might want to ask yourself what your motives are in sharing your thoughts, Simmons suggests. David Berreby, author of Us and Them, an exploration of how and why people split off into groups, agrees. In telling someone what we don’t like about the way she looks, we may also be sending a signal that she’s pushing the boundaries of what’s acceptable for our social group, warning her that she’s not looking like “our kind of people.” An acquaintance of mine invited a friend to a fancy dinner party and was horrified when her friend showed up in a tight, garish dress and “hooker” heels. She didn’t say anything—what was the point?—but was deeply embarrassed. Her friend’s appearance suggested that she, by association, had bad taste, says Berreby. We’re constantly (often unconsciously) classifying people based on the way they look. So when a friend makes an aesthetic choice that suggests vulgarity or coarseness, our investment in telling her what we think might be anchored in our own need to be well regarded. To paraphrase Aristotle, we see ourselves in our friends. And if our friends look like hookers? Our selves might not be comfortable with that.

A Boston woman I’ll call B., who (wisely) declines to be identified, says, “Most of my friends dress badly, wear the wrong makeup, and have terrible haircolor.” B. would readily admit that she’s no style maven, but she tries to cultivate a look that communicates a certain thoughtfulness about the way she puts herself together. She wishes her friends shared this thoughtfulness—they’d look so much better!—and doesn’t understand why they don’t. So she’s motivated to give them a little style assist.

“I close my eyes and see a huge gallery of faces of women I’d like to help,” she says. When one of her particularly dowdy friends said she was going shopping to buy a dress for her daughter’s wedding, B. jumped at the opportunity. “I’m going with you,” she said, and both B. and her friend were delighted with the results. (Though the dress was a success, the friend did wear hideous shoes to the wedding, B. sadly reports.) “I’ll never make a suggestion unless there’s an opening,” she says. “But if a friend who typically wears awful, clunky flats happens to say that she likes my shoes, I’ll say, ‘Thank you. You wouldn’t believe how incredibly comfortable they are. I was surprised that you can actually find stylish shoes that are comfortable, but it’s entirely possible!’” B. also advocates giving gift certificates to a good salon for friends who could use hair help.

On the other hand, Gayle’s more direct modus operandi does work fine for a few bold people. “The best advice I ever got was from a close friend I hadn’t seen in several years,” says one woman. “The first thing she said when she saw me was, ‘Darlin’, I adore you, but you’ve got to do something about that awful, flat haircolor.’ Then she proceeded to send me to her colorist, who did a beautiful job. I was enormously grateful.”

“It’s nice to have a friend who can speak honestly but tactfully to you,” says Valerie Steele, director of the Museum at the Fashion Institute of Technology. But it’s wise to lay down the ground rules of your friendship before a situation like an unlovely dress or a towering hairdo arises. Say you and your sartorially unpredictable friend are having a drink. You enjoy her company and you want to invite her along to cocktail parties and picnics. But you’d also like to feel confident that she won’t show up in something that might get you both arrested. With the diplomatic skills of Talleyrand, you say, “Honey, will you tell me the truth when you think I’m wearing too much eyeshadow or the wrong color lipstick or my skirt’s too short? Sometimes I wonder whether I’m overdoing it with the blush.” If you’re lucky, she responds, “Well, of course, it’s only my opinion, but yes, I will, and won’t you please do the same for me?” Then at the next opportunity you can graciously get down to the business of telling her what not to wear. But what if she stares at you, wide-eyed and open-mouthed, as if you were speaking an obscure Turkish dialect? Take a deep breath, pray that she doesn’t show up at the company softball game looking like Dame Edna, and release yourself from the responsibility of setting her straight.