Spacious 6-Bd. Center-Hall Colonial with Large Terrace & Level, Grassy Yard    This spacious 6-bedroom, 3.5-bath, powder-blue clapboard Colonial-style house was built in the 1930s. Set on a third of an acre with a welcoming semi-circular driveway, it enjoys a large and inviting side terrace and a fenced, grassy backyard - perfect for al fresco dining and entertaining.    Standout features include: an entry vestibule with powder room and coat closet; center hall with coffered ceiling; living room with wood-burning fireplace and door to 29-by-9-ft. terrace with steps to yard; formal dining room with 2 built-in china cabinets; windowed eat-in kitchen; finished walk-out basement with recreation room, laundry and storage areas; private multicar driveways; detached 2-car garage; 0.33-acre lot.    Near Wave Hill public gardens and culture center. Great location for schools, Metro-North trains and express buses to Manhattan.