In a champagne flute, add orange juice and blue curaçao.
Top with champagne.
Garnish with a lime wedge, shamrock or sprig of herbs.
Notes
Substitute pineapple, passion fruit or mango juice for orange juice if needed. If not using blue curaçao, add 4-5 drops of blue food coloring. Use a dry sparkling wine. Champagne, prosecco or cava are all good choices. Look for "brut" on the label.