Preheat oven to 160°C (140°C fan forced). Grease and line 2, 20cm deep round cake pans. Line the bases with baking paper.
Beat cake mix, eggs, butter and milk in a large bowl with electric beaters on low speed for 30 seconds, then on medium speed for 2 minutes. Divide mixture between pans.
Bake for 50 minutes, or until a skewer inserted into the centre of each comes out clean. Cool for 10 minutes in pan, and then gently remove from pans onto a wire rack. Cool completely.
Slice each cake in half through the centre to give four discs. Gently slice off any doming so the discs are flat. Place a disc onto a turn table or cake stand. Spread cake with some frosting. Repeat, ensuring each disc is sitting evenly on top of the one under it. Frost top and whole cake with more vanilla frosting in a thin crumb coat. Chill. Frost whole cake again more generously. With some remaining frosting, using the back of a teaspoon, make some flicks or brushstrokes along the base of the cake. You don’t have to go the whole way around, just do the front if you prefer.
Divide half of each of the remaining two tubs of frosting into four bowls. Add 2 drops of gel colour to each bowl. Mix well. Add an extra drop for a more intense colour. If you are working in a warm environment, chill these.
To create petals, allow a teaspoon for each bowl of coloured frosting. Place some frosting on the back of the teaspoon and spoon onto the cake like a brush stroke. Repeat in choice of design around the sides and top, leaving some white frosting for contrast.