Make the funfetti cupcakes:

1. Preheat the oven to 350°F. Line a 12-cup muffin pan by with cupcake liners. Set aside.
2. In a large mixing bowl, use a hand mixer to cream butter and sugar together on medium-high speed until light and fluffy, about 3-4 minutes. Add in eggs and vanilla, and beat until well incorporated and smooth.
3. In a separate medium-sized mixing bowl, add flour, baking powder, and salt. Whisk together to combine.
4. Add 1/3 of the flour mixture to the large bowl and mix on low speed until combined. Add ½ of the milk and mix on low until combined. Continue alternating the flour and the milk, until both have been completely added (finishing with the flour mixture). Use a silicone spatula to fold in the sprinkles.
5. Use a cookie scoop or spoons to evenly disperse the batter into the cupcake lines, filling them about ¾ full. Place the pan in the oven and bake for 20-22 minutes, or until a toothpick inserted into the middle of one of the cupcakes comes out clean.
6. Allow the cupcakes to cool for 5 minutes in the pan, then transfer them onto a wire cooling rack to cool completely. Allow to cool completely before frosting.

Make the buttercream frosting:

1. In a stand mixer fitted with the whip attachment, add the butter and beat on high speed until fluffy and pale, about 5 minutes (you can also use a hand mixer and large mixing bowl). Turn down to low speed, and begin adding the confectioners' sugar. Once all of the sugar has been added, add the vanilla and salt, then beat on high until very smooth and fluffy, about 2 minutes.
2. Divide the frosting up into 3 mixing bowls. Add a quarter of the frosting to a small mixing bowl (for the white buttercream). Evenly divide the remaining frosting into 2 large mixing bowls (for the red and green buttercream).
3. Add red food colouring to one large bowl and beat to combine. Add green food colouring to the other large bowl, and beat to combine.

Transfer buttercream into piping bags:

1. For the red frosting: Add three-quarters of the red frosting to a large piping bag fitted with a large round tip (Atecco 808). Add the remaining quarter to a small piping bag fitted with a Wilton 68 tip.
2. For the green frosting: Add three-quarters of the green frosting to a large piping bag fitted with a large Wilton 1M tip. Add the remaining quarter to a small piping bag fitted with a Wilton 32 tip.
3. For the white frosting: Add three-quarters of the green frosting to a large piping bag fitted with a large round tip (Atecco 808). Add the remaining quarter to a small piping fitted with a Wilton 18 tip.

Decorate the Christmas cupcakes:

1. Christmas tree cupcakes: Using the large piping bag with green frosting, pipe a tall tree shape on top of one-third of the cupcakes. Carefully insert a gold star cupcake topper on top of the tree all the way so that you can no longer see the toothpick. Sprinkle with rainbow confetti sprinkles on top. You can also dust some confectioners' sugar on top to look like snow.
2. Santa hat cupcakes: Using the large piping bag with red frosting, and pipe a swirl of frosting onto another one-third of the cupcakes. Using the small piping bag with white frosting, pipe small stars around the bottom perimeter of the red swirl. Finally, use the same bag to pipe a small dollop onto the top tip if the frosting, then lightly use your finger to press down any edges to make it look more ball/round like.
3. Wreath cupcakes: Using the large piping bag with white frosting, pipe a small round circle of frosting onto 1/3 of the cupcakes. Using the small piping bag with green frosting, pipe a wreath shape on top of the white frosting. Using the small piping bag with red frosting, pipe a bowl shape at the top of each wreath. Lastly, sprinkle with rainbow confetti sprinkles.