A group of reporters was interviewing Henry Green, the co-owner of Preakness candidate Partez, when a New York Timesman approached and turned on his tape recorder.

Greene looked at him sternly. "You haven't paid the commission," he said.

The Timesman produced a quarter and handed it over but said, "I need something exclusive for this." Green obligingly whispered a few words in the reporter's ear as he happily pocketed his profit for the morning.

Henry Greene understands the value of a quarter, and a dollar, and expecially the $197,800 that will go to the winner of Saturday's race at Pimlico. While this money might be inconsequential to sportsmen like Thomas Mellon Evans and John Hay Whitney, who own the two favorites for the race, Greene said, "You don't get into the horse business for no hobby. You don't pay $60,000 for no hobby." His partner, Elizabeth Davis, added, "This horse has to pay his own way."

Greene's background is a trifle different from the Mellons and the Whitneys. His father had walked out of the house when he was 3 months old, and his mother worked in the fields of Port Gibson, Miss., picking cotton for 50 cents a day to support her family. Henry's first job was to carry water to the cotton-pickers; he made $1.50 a week. He worked in a meat market and saved enough money to start his first business, although there weren't many business opportunities for blacks in Mississippi during the Depression. He opened a little grocery store with a pool hall in the back, and then moved to Kansas City, Kan., where he bought a joint that sold 15-cent hamburgers.

It was in Kansas City that he met his future wife, Annabelle, who promised him, "Stick with me and I'll put your name in lights." The Greenes migrated to California, bought a motel, then built two others, with Annabelle managing the money, writing the checks and dunning the late accounts. "She's a demon bookkeeper," Greene said. "She's tough with a pencil."

The Greenes made enough money in this enterprise that they were able to sell out and retire in the early 1970s. They had enough money to buy a few modest racehorses, with whom they enjoyed modest success. One friend who followed their equine ventures with special interest was their accountant, Elizabeth Davis, a lifelong horse-lover. When Annabelle suggested, "Why don't we get a horse together?" Davis agreed eagerly.

She was no Mellon or Whitney, either. "I'm a working woman with three children in college," she said. "I had a total of $30,000 to invest. I know it doesn't fit the stereotype of an accountant that I would be flaky enough to buy a horse with it, but this was a strong hunch with me. Anyway, I could tell my friends that it was a good tax shelter."

Annabelle Green and Elizabeth Davis picked out a colt whose breeding they liked, and the partnership bought Partez for $60,000 at a sale in California. He repaid this investment quickly, winning a minor stake as a 2-year-old, and then won a grass race at Santa Anita impressively this spring. Even after the colt was soundly beaten in the Santa Anita Derby the owners and trainer Wayne Lukas decided to take a shot at the Kentucky Derby.

Nobody paid much attention to Partez at Churchill Downs, and nobody noticed him during the early stages of the Derby, either. As Greene watched, he told Annabelle, "Honey, he ain't gonna get nothing."

Then, suddenly, Partez began to accelerate from 12th place. Davis' daughter was using the family binoculars and shouted, "He's fourth! He's third!" until her hands started shaking so badly she couldn't hold the glasses straight. When Partez reached the lead as he turned into the stretch, Davis said, "I was jumping up and down and shaking like a leaf, too."

Partez couldn't sustain this run, and he wasn't helped any when jockey Sandy Hawley misjudged the finish line, standing in the irons prematurely. Nevertheless, he managed to finish third, earning $27,500 and a trip to the Preakness.

The type of powerful but abortive move that Partez made in the Derby frequently points out a horse who is about to win his next race. Partez is a strong contender in the Preakness, and if he wins it he will become a very valuable racehorse.

Greene doesn't know much about the nuances of thoroughbred breeding, but he does know the kind of prices that good racehorses command when they go to stud nowadays. "I'd be willing to call it off after this year," he said. "When Partez gets bred, that's when I get into the old rocking chair and just reach into the mailbox to get the checks."