Cream the butter.
Add the sugar and vanilla; cream until light and fluffy.
Add a few drops of food coloring to tint a light green.
Add the flour and pecans; mix well.
Roll into 1-inch balls and place an inch apart on an ungreased cookie sheet.
Bake in a 325° oven for 18 to 20 minutes, or until lightly browned.
Remove from the cookie sheet and roll in confectioners' sugar while warm.