Beat the egg whites with a hand mixer, then gradually add in the sugar and beat until a stiff meringue forms. Carefully beat in the vegetable oil, milk, and flour, adding in the 3 ingredients in 3 different batches. Continue to beat the mixture until a smooth batter forms.
Mix all of the ingredients together, then divide the batter into 3 equal portions. Stir 1 type of food coloring into each portion of batter to create red, blue, and green batters. Transfer all 3 of the colored batters into separate piping bags. Print and cut out the stencils found at the end of this recipe. Grease a baking tray, then line it with parchment paper. Place the stencils on the baking tray.
Pipe the colorful batter into the empty triangles cut out of the stencils, then carefully remove the stencils. Transfer the baking tray to the refrigerator and chill for 30 minutes. Preheat the oven to 350°F. Pour the sponge cake batter onto the baking tray, making sure it covers the colorful cake batter completely. Transfer the baking tray to the oven and bake the mosaic cake at 325°F for 27 minutes. After the mosaic cake has baked, carefully flip the baking tray over onto a clean work surface and peel off the parchment paper. Cut the 2 rectangular pieces and 1 circular piece of colorful mosaic cake out.
Mix together the cream cheese and the sweetened condensed milk. Add in the lemon juice and fold in the whipped cream. Line the ring of a 7-inch springform pan with the 2 rectangular pieces of mosaic cake.
Crush the graham crackers and stir them together with the melted butter. Press the mixture into the base of the springform pan using the bottom of a glass, then transfer the springform pan to the refrigerator and chill for 30 minutes.
Chop the kiwis, then stir together the blueberries, raspberries, and chopped kiwi. Fill half of the springform pan with the cheesecake filling, then spoon the mixed fruit on top.
Pour the rest of the cheesecake filling into the springform pan, smooth out the top, and put the round piece of mosaic cake on top. Lightly press down on the top of the cake, transfer the springform pan to the refrigerator, and chill for at least 4 hours.