F. Hugh Herbert's new comedy, "The Moon is Blue," starts off promisingly enough. The first act is fresh and amusing, and sometimes quite clever. A naive young blonde, played by Barbara Bel Geddes, picks up an architect, played by Barry Nelson, on the observation tower of the Empire State Building. The scene shifts to the architect's home in the East sixties. There young love seems to be blossoming unchecked when a middle-aged, somewhat alcoholic rake played by Donald Cook crashes the party.

But something happens to the comedy between the first and second acts. The last two-thirds of the play contains some of the dreariest, and generally unfunniest talk imaginable. Every once in a while a funny line comes along, but the dullness of the rest of the dialogue is stupefying. Miss Bel Geddes' lines consist of a string of incredibly stupid questions, each of which exasperates Mr. Nelson anew. This is something short of rippling dialogue.

Donald Cook manages to make something quite comic out of his Southern boozehound. His acting is a line job of underplaying and exact timing. If the other stars had the same energetic approach things might be a little more interesting. Neva Patterson appears briefly as a Conover model. Miss Patterson is not only a dazzling woman but a fine actress, and it's too bad that she has been given a part that is poorly written.

Otto Preminger directed "The Moon is Blue," and his efforts, if he made any, are without manifestation. Stewart Chaney's two sets are bright and cheerful, which the play is not. Probably the happiest person connected with "The Moon is Blue" is Barry Nelson. He got married on Monday.