Place the candy melts three microwave safe bowls. Tip: I like to use paper bowls for easy clean up. Melt in 30 second increments, stirring between each, until melted and smooth. If needed, add 1 teaspoon vegetable oil to aid in melting.
Color each bowl a different color with gel food coloring (pink, purple, teal).
Add each color to a small ziploc bag and cut off one tip (or use a pastry bag). Pipe as desired into your mermaid tale molds (either one color per tail or a mix). Scrape off excess and allow to set.
Once the tails are hardened, very carefully remove them from the molds.
Divide frosting into 3 bowls. Color each bowl a different color with gel food coloring (pink, purple, teal).
Lay out a piece of plastic wrap and place one frosting color in a horizontal line. Repeat with second and third colors, making sure the lines touch. Roll up the plastic and twist the ends.
Fit a pastry bag with a 1M (open star) tip. Cut off one twisted end and add to the pastry bag. Squeeze out some frosting until the colors start to swirl.
Frost cupcakes as desired. Sprinkle with sprinkles. Top with a mermaid tail.
Store in an airtight container in the refrigerator for up to 3 days.