Zionsville, a chestnut gelding owned by Mrs. Sylvester Johnson, won the green conformation hunter championship today on the second day of the week-long Upperville Colt and Horse Show. The show is being held at Grafton Farm along Rte. 50 just east of Upperville.

The young chestnut acquired 14 1/2 points by placing in every class in his division. He is ridden by Charlie Weaver and trained by Mr. and Mrs. Kenneth Wheeler of Cismont Manor Farm at Keswick, Va. The Johnson-Wheeler-Weaver combination has already compiled a large number of ribbons at the show. Fun and Games and Super Flash, who was named reserve champion regular conformation hunter, also have scored successes for the trio.

Jane Gaston rode Betty McGuire's bay gelding Harvard Square to take the reserve in the green conformation division. Chadds Ford, owned by Mr. and Mrs. Martin O'Rourke of Sewickley, Pa., and ridden by Brian Lenehan, earned the tricolor over Super Flash in the regular confirmation section.

Nina Fout, 1979 U.S. junior threeday event champion, rode her parents' Dynaman to capture the local hunter championship.

Speculation, with Foxlore Farm of Middleburg as agent, won the reserve championship in the local section with Allen Smith up.

More than 750 horses and ponies will be competing the rest of the week. The show concludes Sunday with the $15,000 Upperville Jumper Classic, which begins at 2:00 p.m., and is sanctioned by the Amerian Grand Prix Association.

Thursday's program features preliminary, intermediate and open jumpers as well as small amateur-owner and green working hunters.