The funniest, most colorful and most touching tennis player among the women at the championships of Wimbledon is Martina Navratilova.

But it's a secret.

Americans like little girls from Fort Lauderdale, Fla., or Rolling Hills, Calif., who have ribbons in their hair or wear pinafore dresses until they're old enough to vote. Americans like cute, unthreatening women tennis players who make genteel noises when they play.

Thus Americans, as yet, don't seem to know what to make of Navratilova. Her game is power, so they don't notice here delicacy at the net, her grace in prowling the court. Her speech still has the Czechoslovakian accent of her native land, so the wit in her comments is sometimes overlooked.

Perhaps worst of all, Navratilova has muscles and a name that, to American ears, sounds harsh and foreign rather than lilting like, perhaps, Goolagong.

So, Martina is the great player who doesn't get cheered a great deal. She has chosen America, embraced it, but she has not gotten warmth in return.

On Wednesday here, Navratilova will play 18-year-old Hana Mandlikova, the current pride of the Czechs, in the semifinals. Only one thing would suit Navratilova better: if it were the final.

"I can't wait," Navratilova said, "because now the Czechs will have to report the results. Because I am playing Hana, they cannot pretend that I no longer exist.

"It would be even more fun in the final because then it would have to be on TV in Czechoslovakia. My parents could see it. Everybody would see," she says.

"It would be interesting, because, if she beats me, there you go, they'll say I lost because I left the country and came to America. They'll play it up for all it's worth."

Navratilova knows what it means, far more than most people, to be torn in two directions.

"I have nothing against Hana.I've known her and her parents since she was a little girl kicking a soccer ball beside the courts where we played. When she was 10 or 11, she was my ball girl at matches," said Navratilova.

"But I can't be indifferent to how I'm seem in the country where I was born (and lived until she defected in 1975 at the age of 18). I am Czech . . . Or I was Czech . . . or whatever I am."

Navratilova is not yet an American citizen: that comes later this year. But she is American in spirit.

"I regret some things I have done in my life," she says, "but coming to the States will never be one of them. I love it."

Navratilova was at her charming best at match point today against Virginia Ruzici, whom she beat, 6-2, 6-3.

On that final point, Navratilova threw both arms into the air and let go of her racket. All she neglected to note was that Ruzici had reached the ball and hit it back over the net.

Navratilova bobbled her racket, grabbed it and swatted the ball into an open court for the winning point.

Then, her face lit up in a spontaneous smile of delight and embarrassment at the ridiculousness of her premature celebration.

"That was a helluva match point, wasn't it?" she said sheepishly afterward. "I swore I saw the ball bounce twice, but it was my overactive imagination. Thank God she didn't hit a winner while I was standing there in my victory pose.

"When I see that point on TV tonight, I'll still think she won't get to that ball."

In a sport full of prim, proper, parent-ruled players, Navratilova is a woman who has had to figure out everything for herself in a strange land with her family left behind. These days are doubly hard for Navratilova because, through no doing of her own, she has become a symbol. When Billie Jean King admitted to her lesbian affair with a former secretary, the line of journalists began forming in Navratilova's wake to hector her about her thoughts on the matter.

Navratilova's companion, with whom whe owns an old home in Charlottesville, Va., is author Rita Mae Brown, who wrote the bestseller Rubyfruit Jungle and who, in recent years, has been a gay activist.

Navratilova, as might be expected, answers directly when asked how she feels about King's presence here as sort of politely ignored nonperson. Even though King has won 20 Wimbledon titles, more than any other person, her retirement from this event, and perhaps from her sport, has gone without the sort of sentimental farewell-and-thanks that has been allotted to Virginia Wade in recent days.

"It's like Billie Jean isn't even here (as a television commentator)," said Navratilova. "It's sad that she's going out this way. Since nothing was said about her, I just assumed that she was playing in the doubles."

At this Wimbledon, Navratilova has practically had a monopoly on quickwitted quips. Asked why she's playing so well, she says she's learned to relax in the mornings by doing the laundry. To her many superstitions, she's added one: "Since Borg never shaves during Wimbleton, I'm not going to, either."

A hard, dark tinge surrounds Navratilova's humor. She is a woman between countries, officially despised as a counter-revolutionary in one and often ignored in the other. Her face is gentle, thoughtful, amused, sometimes hurt. iBut it doesn't have that all-American carbonated smile.

Navratilova has committed the cardinal sin of athletic superstardom. She's labored hard to become a person but hasn't yet gotten around to working on a palatable image.

Today, someone asking a casual question referred to Navratilova as graceful.

"I don't often hear myself called that," she said, "although I think of myself as graceful. I don't get as much credit for that as others do."

There are many things for which Navratilova does not get credit. At every turn, she has gone through more, endured more, faced harder, more tormenting problems than her peers. Yet she has emerged from it with an almost defiant cheerfulness.

"When you think of the world," wrote the satirist Jonathan Swift, "give it one lash the more, with my regards."