Heat oven to 400°F. Combine butter, sugar, egg and extract in mixer. 

Blend at medium speed, scraping bowl often, until creamy. Add flour and salt, and blend at low speed until well mixed. Divide and use food coloring by mixing in each color.

To make the cookies, insert a 1M tip into pastry bag. Fill bag with cookie dough. If it's hard to pipe add the 1 tablespoon water. Warming the piping bag with your hands will help to pipe out the cookies. Do this in a rotated motion on to a baking sheet lined with parchment paper.

Bake for 5 to 8 minutes, or until slightly golden. Remove to a cookie rack and let cool. Once cool fill with jam or filling of choice.