Heat oven to 350F and place rack in center. Line two baking sheets with parchment paper.

In a large mixer bowl, beat together butter, cream cheese and granulated sugar until light, about 2 minutes. Beat in egg and zest until combined well. Stir in flour and salt until a dough forms.

Halve dough; stir a few drops of food coloring into one half. Transfer some of each dough color, side by side, to a decorating bag fitted with a 1/2-inch plain tip or coupler. Pipe 4-inch-long tree shapes, 1 inch apart, on prepared sheets, bottoms facing 3 to four inches from outer edge. Insert sticks halfway through bottoms. Bake, one sheet at a time, until just golden around edges, 15 to 18 minutes. Transfer sheet to a wire rack and let cool completely.

Whisk together confectioners' sugar and juice. Drizzle over each tree; sprinkle with sanding sugar. (Store in an airtight container at room temperature, in single layers, up to 2 days.)