Cut the sponge cakes in half lengthwise and fit the bottom halves into a 7 by 11-inch pan. Drizzle half the coffee over them.
Whip the cream to soft peaks and sweeten it with the sugar. Whisk the mascarpone cheese a bit to loosen it and fold in the whipped cream. Pour half of this mixture over the sponge cakes and spread it out evenly. Make another layer with the tops of the sponge cakes and drizzle them with the remaining coffee. Mix about 10 drops of food coloring into the remaining cream mixture, enough to make it the same yellow color as the sponge cakes. Spread this evenly over the sponge cakes. Coarsely crush the vanilla wafers and scatter them over the top. Cover and refrigerate for at least 2 hours before serving.