In a large bowl, cream butter and cream cheese. Add sugar and vanilla. With an electric mixer at medium speed, beat until light and fluffy.
In medium sized bowl, combine flour and salt; gradually adding to creamed mixture, beating until well blended. Stir in chopped pecans. Cover bowl with plastic wrap and refrigerate for 15 minutes.
On four sheets of aluminum foil, shape dough into four 6-inch rolls, 1 1/2 inches in diameter. Wrap each roll tightly in foil and refrigerate overnight.
Preheat oven to 325°. Line cookie sheets with foil. Remove rolls of dough from refrigerator one at a time. Coat each roll with red or green sugar crystals. Cut dough into 1/4 inch slices. Place on prepared cookie sheets; top each cookie with a pecan half. Bake for 15-18 minutes or until bottom of cookie is lightly browned when lifted.