Using a toothpick, add desired food coloring to a portion of Italian meringue buttercream. Transfer buttercream to a piping bag fitted with desired piping tip. Use a dough scraper to push the buttercream towards the tip. Tie up the bag and trim the end. Cut around the piping tip and tear away the plastic. Pipe a small dot of buttercream onto a piping nail. Stick a small square of parchment paper on top.
To make buttercream roses, use piping tip 125. Create the base by piping a small cone in an upward, wavy motion. With the piping tip tilted to the side, create the innermost petal by piping an almost closed circle. Rotate the piping nail continuously and gently squeeze the piping bag to apply even pressure. To create the next petal, pipe the first petal in a rainbow motion. Pipe each petal so that it slightly overlaps the previous petal and continue this method for each petal until you have a full rose.
To pipe buttercream peonies, use piping tip 123. Create the base by piping a small cone in an upward, wavy motion. Use piping tip 0 to pipe the stringy center of the peony in swift upward motions. Use piping tip 123 to begin piping the petals around the center in rainbow motions. Rotate the piping nail continuously and gently squeeze the piping bag to apply even pressure. Pipe each petal so that it overlaps the previous petal. Continue until you have a full peony.
To pipe buttercream dahlias, use piping tip 79. Pipe a ring of buttercream, followed by a second ring on top. Rotate the piping nail continuously and gently squeeze the piping bag to apply even pressure. Beginning around the inside of the ring, pipe consecutive petals in swift upward motions. Pipe the innermost layer of petals in the gaps between the first ring of petals. Next, pipe petals around the outermost ring. Continue piping in this pattern until you have a full dahlia. Use piping tip 0 to pipe the stringy center of the dahlia in swift upward motions.
Before decorating a cake with buttercream flowers, chill them first in the refrigerator. Place the buttercream flowers snugly together on top of the cake. Pipe a small amount of buttercream to help attach flowers stuck on at an angle. If desired, use tip X to pipe leaves around the flowers. Alternatively, pipe extra flower petals to peer out from around the full flowers.