Cut pound cake crosswise into seven 1-inch slices. Cut each slice into 6 square pieces. Line a baking sheet with wax paper. Place 1/4 cup frosting in a resealable plastic bag, and snip off one tiny corner. Divide remainder among 3 small glass bowls. Tint 1 bowl with rose icing color and 1 with violet, and leave 1 white. Microwave one bowl for 10 to 15 seconds, until the consistency of heavy cream.
Using a fork, dip a cube of cake into warm frosting, coating top and sides. Let excess frosting drip back into bowl. Using another fork, slide frosted cube onto wax paper; scatter top with sprinkles, if using. Repeat with 13 more cubes. Heat second frosting bowl and dip 14 more cubes; dip final group of cubes into last frosting bowl after heating. Using frosting in plastic bag, pipe desired messages onto cubes. Serve cubes in candy liners.