In a saucepan, combine 3 cups filtered water with sugar. Stir in butterfly pea flowers. Bring to a simmer. Remove from heat, cover and let steep for 10 minutes. Strain through a fine mesh sieve, discarding solids. Set aside to cool.In a jar or glass measuring cup, combine lemon juice and remaining 2 cups of water.To serve, fill glasses with ice. Pour cooled butterfly pea syrup into glass, filling about half way.Pour lemon mixture over top, and watch the magic happen! Where the lemon meets the syrup, the color will change from blue to pink. Stir to combine the two mixtures until the color is pink throughout and enjoy!