Preheat your oven to 350°F (175°C). Line two baking sheets with parchment paper or silicone mats.

In a medium bowl, whisk together flour, baking powder, salt, cinnamon, and nutmeg. Set aside.

In a large bowl, beat softened butter and granulated sugar on medium speed until light and fluffy, about 2 to 3 minutes.

Beat in eggs one at a time, then mix in vanilla extract and orange zest.

Gradually add the dry ingredient mix to the wet, beating on low speed until just combined. Avoid overmixing.

Scoop tablespoon-sized dough balls onto prepared baking sheets, spacing about 2 inches apart.

Bake for 12 to 15 minutes, until edges are lightly golden but centers still look soft.

Let cookies cool on baking sheets for 5 minutes, then transfer to wire racks to cool completely.

While cookies cool, whisk powdered sugar with milk and vanilla extract until smooth.

Divide into three bowls and tint each bowl with gel food coloring: one purple, one green, one gold/yellow.

Drizzle the three icing colors onto each cookie and swirl gently with a toothpick or small spatula.

Allow icing to set at room temperature for about 30 minutes before serving or storing.