Spread seeds in a 4-sided sheet pan and toast in oven until puffed and slightly golden (but not browned), 6 to 8 minutes. Cool completely on a plate.
Stir 1/4 teaspoon colored powder into 1 teaspoon water in a small bowl until dissolved.
Spread 10 wafers in 1 layer on a rack. Paint tops of wafers lightly with coloring using a pastry brush (for white wafers, brush with water).
Let stand until pliable, 3 to 5 minutes (if too wet to lift, let stand until slightly drier). Invert wafers, then spoon a level teaspoon dulce de leche onto unpainted side of each. Fold each in half, pressing to spread dulce de leche just to edge. Insert 8 seeds halfway into dulce de lechedulce de leche is firm enough to hold seeds in place, 1 to 4 hours.
Meanwhile, paint remaining wafers with remaining colors, 1 color at a time. Make more confections in same manner.
•Confections keep, stacked in an airtight container at room temperature, 1 week. •
Mixed colored half-moons can be packaged in clear cellophane bags tied with ribbon.
