Youthful verve and a mod musical, "Joseph and the Amazing Technicolor Dreamcoat," an ideal vehicle for the young, begin the Olney Summer Theater season. This bright novelty is by Tim Rice and Andrew Lloyd Webber, creators of "Jesus Christ Superstar."

With a couple of exceptions, this is the same cast which recently packed Catholic University Hartke Theater. It's novel to start Olney's season with a student production, but director James D. Waring's choice is justifiable because it works delightfully. This is a more spontaneous, innocent little show than the team's famed "Jesus Christ Superstar."

Olney, beginning its 40th summer, was instituted by the late Steven Cochran as a "countryside" home for the stock companies he presented a manager of the National Theater. When Ethel Barrymore, his longtime employer, opened his house in 1938, Olney was the sole professional summer theater south of the Mason-Dixon line. Now, in its 26th season under the management of the professional National Players, Olney is one of many. The population of the area has increased vastly, but Olney remains as lovely a "countryside" as it was then.

The accent this season is on youth. Drawn from the Genesis chapters on Jacob's favorite son, Joseph, a varied series of Rice-Webber songs traces the story about the envious brothers who sold Joseph into slavery in Egypt. Joseph's ability to explain Pharoah's dreams nets him the post of Egypt's second-in-command and reunion with Jacob.

Their variety of songs quickens the Rice-Webber score-recitatives, ballads, calypso, Country-Western, Parisian apache, gospel shouting and lusty male and female choruses. Kevin McCarthy leads his eight-piece, on-stage band through a malange of rhythms.

It's hard to imagine a more fitting Joseph than Mark Heckler, whose guileless, All-American boy looks are matched by effortless voice and style.

Ayl Mack's important role of singing narrator is distinguished for his diction, truly first-rate. As the hip-gyrating Pharoah, Blaise Corrigan, new to the cast, is splendidly amusing. Move over, John Travolta, Corrigan's on his way.