Prep the Frosting: You'll need to create six colors: white, black, tan, light blue, medium gray-blue and dark blue. Reserve 3 cups for the blue details; the other cup can be divided first in half—with half going to the tan color, and the remaining half split to become the white and black shades.
Place the white frosting into a piping bag or resealable bag and set aside.
Create the Black Frosting: In a small bowl, add vanilla frosting and a couple drops of black food coloring at a time, stirring until you reach the shade you want. Place in a piping bag or resealable bag and set aside. If you have a small round piping tip—with a hole about the size of a Magic Marker—use that for the black icing, or try cutting a hole about that size into your plastic baggie when the time comes.
Create the Tan Frosting: In another small bowl, combine the vanilla frosting with half a drop of yellow and the tiniest smidge of red—I dipped a toothpick into red to get the tiniest amount at first—stirring to create a tannish orange color. (You may need to add vanilla if it turns out too orange-y at first.) Gradually add color until you get the hue you want, then bag it up. (NOTE: You can skip the mixing and get a very reliable tan if you use tan or copper gel food coloring instead; it can just be harder to find.)
Create the Pale Blue Frosting: Place the 3 cups of frosting for the blue tones in a large mixing bowl. Add 2-3 drops of blue, stirring until you have a light sky blue. After you've used this to frost the head, we'll return to this bowl and the remaining frosting within it to create the darker shades!
Shape Bluey's Head: Take the 9"x13" cake and cut it widthwise, creating two 9"x6.5" rectangles. Set one on a cake stand or large plate to be the base of Bluey's head. We'll use the other to create the snout and ears.
Create Bluey's Snout and Ears: Cut two 3" strips to form the snout, and use the remaining piece to cut out two triangles for the ears. You'll place one snout piece next to the rectangular cake, frosting the whole thing in pale blue, then place the second snout piece on top and frost that. This gives the snout a more 3D effect. (Before placing the top piece, I also carved the left side, so it looked more like a wedge. That way it'd be more flush with Bluey's head, gradually sloping upward once frosted.)
Frost Bluey's whole head pale blue. With the remaining frosting, set aside about 1/4 cup for the medium blue, placing it in another small bowl. Add a tiny drop of black gel food coloring—or squirt a tiny bit of black frosting—and stir together to create a slightly darker, almost grayish-teal shade. Place in a piping or resealable bag.
Use the rest to create the dark blue shade right in the mixing bowl, adding a couple drops of blue food coloring, stirring in between, until you reach your desired shade. Place in a piping or resealable bag.
Decorate Bluey's Face: I started with her dark blue ears, patches around her eyes and nose, piping the color on and then smoothing it with a butter knife. (An offset spatula works too!) Then, I added large white eyes, then filled in the tan inner ears and snout, before drawing Bluey's medium-blue stomach and eyebrows.
Add Bluey's smile and pupils with black frosting. That's it! You did it!
