In the spirit of Halloween, Debbie Dolan and Mario Deslauriers dressed up as crayons. But they had no time to trick or treat because they were busy winning the $12,500 International Open Jumper pair relay event at the Washington International Horse Show at Capital Centre last night.

Competing against 14 other costumed pairs over the nine-fence course, Dolan, riding Lucas, and Deslauriers on Paulyes finished with the fastest time of 55.61 seconds.

To win, each team goes through the course twice, sharing jumps in the fastest possible sequence.

Rodney Jenkins and Lisa Jacquin rode Potluck and Ingo, respectively, to second in 58.03.

The husband-and-wife team of Henri Prudent (riding Pensato) and Katie Monahan Prudent (on Make My Day) completed the fastest round in 54.36 seconds, but four seconds were added for a fault at the 15th obstacle to gain third place.

James Benedetto and his 8-year-old Neat 'N Sweet scored four faults in 53.77 in a two-horse jumpoff round to win the $10,000 Insilco Amateur Owner Jumper Classic over 34 other entries.

The victory also gave the 23-year-old Northport, N.Y., native top honors in a year-long, 13-event series of jumping competitions. Benedetto, a runner-up in the series in 1985, scored 136 points to win the amateur owner title by six points over Amy Brumder, riding Radetsky.

"I knew I had to win {yesterday's event}," said Benedetto, who plans to join the pro show jumping circuit next year. "To have to win is the most pressure."

The President's Cup Grand Prix today in the show's final program will be the last chance for the U.S. Equestrian Team to beat the French in individual competition.

France has won the team competition with 57 points. The USET has 26 points. In winning four of five jumper events this week, the French team has proved dominant in international events. The Grand Prix will give Rodney Jenkins of Rapidan, Va., the opportunity to improve his lead in the rider-of-the-year standings.