Heat oven to 350°F (325°F for dark or nonstick pans). Place paper baking cup in each of 24 regular-size muffin cups. Make and bake cake mix as directed on box for 24 cupcakes. Cool in pans 10 minutes; remove from pans to cooling rack. Cool completely, about 30 minutes.
By slowly moving end of round handle of wooden spoon back and forth, make deep, 3/4-inch-wide indentation in center of top of each cupcake, not quite to bottom (wiggle end of spoon in cupcake to make opening large enough).
In medium bowl, beat lemon curd and cream cheese with electric mixer on medium speed until blended. Spoon into small resealable food-storage plastic bag; seal bag. Cut 3/8-inch tip off 1 bottom corner of bag. Insert tip of bag into top of each cupcake; squeeze bag to fill cupcake.
Stir 4 drops food color into frosting until pale yellow. Frost cupcakes.
Place unopened icing tube in tall drinking glass filled with hot tap water for 15 minutes. Remove from water; wipe dry. Knead tube gently with hands to soften. Using leaf tip on icing tube, pipe 2 concentric circles of leaves, starting with outside edge of cupcake and working toward center; leave quarter-size area in center with just frosting. Carefully spoon 1 teaspoon chocolate chips onto center of each cupcake; press into frosting. Arrange on tray using sour candy straws for stems and leaves. Refrigerate until ready to serve. Loosely cover and refrigerate any remaining cupcakes.