Maybe she though he had bought a blue drink for her

http://images.google.com/images?hl=en&fkt=1247&fsdt=3678&q=blue%20drink&um=1&ie=UTF-8&sa=N&tab=wi

Blue Hawaiian:
2 oz. Malibu Coconut flavored rum
½ oz. Blue Curaco
3 oz. Pineapple juice
1 oz. coconut cream
Pineapple slice
Maraschino cherry

In a cocktail shaker ½ filled with ice, pour Malibu coconut flavored rum, Blue Curaco, pineapple juice and coconut cream. Shake 3-5 seconds and strain into a highball glass ¾ filled with ice. Garnish with a pineapple slice and maraschino cherry.