The yellow slicker—that traditional uniform of the deckhand—is getting a lot of competition this summer. Wherever East Coast sailors put to sea, lightweight parkas made of India madras, wool melton and nylon sailcloth are replacing oilskins and sou'westers. Bold-patterned madras, impregnated with vinyl for water-repellency, is already the most colorful favorite. Here, in photographs taken on a racing weekend at Larchmont, Bob McLaughlin (at top) wears a new vinyl-madras slicker top, this one by Holt, Knowles of Miami ($22.50 at Lord & Taylor). At bottom right, Dick Egan's navy-blue sailing shirt is made in Sweden of water-shedding lightweight wool, long preferred by Scandinavian sailors, with traditional brass buttons at the neck. Iselin imports the shirt ($37.50 at the Sacred Cod, Gloucester). Sandy McLaughlin, furling the mainsail at bottom left, wears a blue-and-white parka that is sail-stitched in the same heavy-duty nylon as the sails themselves. M.J. Manufacturing Co. makes them up in bright stripings to match the spinnakers and mainsails of almost all boats ($13 at Northeast Sailmakers, Boston). These parkas are also finding favor with galleymates; all three are available in small sizes.