Horror is a staple at most video stores, where shelves are clogged with a steady flow of low-budget slash-and-splatter epics. But this month brings an alternative to the standard video blood bath in the form of a bumper crop of classic horror films fresh from the studio vaults. These late-show staples are sure to spark the Halloween spirit in even the most fainthearted: Most are shot in monochrome, in which blood, like the omnipresent fog, is just a discreet shade of gray.

The granddaddy of the genre, Universal's 1931 "Frankenstein," is just out on tape in its original, uncut version. This wasn't the first screen adaptation of Mary Shelley's story, but it was the first that spoke, and the first that featured Boris Karloff, whose career it transformed. A number of scenes cut from the original theatrical release and missing from previously available videocassettes have been restored, most notably Frankenstein's line comparing himself to God and the scene in which the monster tosses the little girl into the lake, which was reportedly excised because Karloff's visible concern at his misdeed rendered his characterization too complex. There's also an introduction by actor Edward Van Sloan (who plays the monster's first victim) that offers a "friendly warning" to viewers who "do not care to subject {their} nerves to such a strain" as the terror that follows.

Universal affiliate MCA Home Video is listing the tape at $29.95, which is also the price of "The Wolf Man," another relic from the studio's horror heyday that is now making its debut on tape as part of the Gene Shalit's Critics' Choice line. This 1941 outing features Lon Chaney Jr. in the title role, with Claude Rains as his father and Bela Lugosi as the werewolf gypsy fortuneteller whose bite does Chaney in.

Universal, which was also responsible for "Dracula," "The Bride of Frankenstein," "The Mummy," "The Phantom of the Opera" and "The Invisible Man" (all of which are available on tape from MCA), has more horror classics in its crypt than it can manage, and has thus licensed some of its lesser gems to discount video suppliers -- a boon for budget-conscious horror buffs. Good Times Home Video has two monster movie milestones coming out this month at prices below $10: "It Came From Outer Space," from 1953, and "The Creature From the Black Lagoon," which followed one year later. Both are available only on VHS.

Universal's virtual monster monopoly did not prevent other studios from feeding '30s audiences' insatiable appetite for terror, and MGM-UA Home Video has a handful of new rental titles from that era. Director Tod Browning's "Freaks" (on tape since last year) proved too much for Depression audiences, who stayed away from its real-life freak show, but his subsequent, slightly more mainstream efforts found wider acceptance. This month brings two Browning chillers starring Lionel Barrymore: "The Devil Doll" (1936), in which Barrymore, dressed as an old woman, miniaturizes his enemies with an evil serum, and "Mark of the Vampire" (1935), costarring Lugosi. And before Michael Curtiz directed "Casablanca," he was one of the first filmmakers to experiment with the early two-color Technicolor process, which he used in two "long lost" giants from the horror canon: "Doctor X," the 1932 film that marked Fay Wray's screen (and scream) debut, and "The Mystery of the Wax Museum" (1933), in which Wray flees a mad sculptor whose body of work is really corpses at the core.

Finally, also from MGM-UA comes "Donovan's Brain," in which a long-suffering wife must save the world from her megalomaniacal husband's mad experiment. The 1953 film was a remake of 1944's "The Lady and the Monster," but it may be of greatest interest today because of its leading lady: Nancy Davis, who had married Ronald Reagan the year before.

'Platoon' Goes AWOL "Platoon," which was scheduled for release yesterday, has hit a snag. HBO Video had already started shipping some of the 350,000 copies of the video it had sold when the 9th U.S. Circuit Court of Appeals unexpectedly reversed itself and granted Vestron Video's request for an injunction against tapes of both "Platoon" and "Hoosiers," a September release that has been ordered removed from retailers' shelves. The freeze will stand until the court decides on HBO's request for a reversal of the injunction and Vestron's charge that HBO Video is infringing on Vestron's copyright on the two movies. The delay that will result from this about-face will depend in part on which company prevails. HBO says that it could have the tape in stores within a matter of days after the court's decision, while Vestron will require a month if the court finds in its favor.