Prepare dough for Favorite Cutout Cookies. In step 2, roll dough 1/4 inch thick. Cut cookies into desired shapes and bake as directed until golden, 15 to 18 minutes. Transfer the cookies to racks and cool until just warm to touch.
Spread each cookie with plain white or palely tinted powdered sugar icing for spreading (recipe below). Let icing dry until hard, about 4 hours.
To paint cookies, put undiluted food coloring in small individual bowls; for less intense color, dilute with a little water. Use watercolor brushes to paint designs on iced cookies. The food coloring will spread, so leave a little space between colors or allow each color to dry before painting with another.
Powdered sugar icing. Controlling consistency of icing is simple. If it's too thick, add a few drops of water; if it's too thin, gradually add more powdered sugar. To tint, add food coloring a few drops at a time.
For spreading: In a bowl, stir 3 cups powdered sugar, 1 teaspoon vanilla, and 1/4 cup water until smooth. Tint with food coloring as desired. Spread icing onto cool cookies with a metal spatula. Let stand until icing is firm, about 1 1/2 hours. Makes about 1 cup.