People often find menstrual topics funny, probably because they are difficult to talk about.
The British and French ads here show a playfulness, but based on the desire to conceal what the products really are. Interestingly enough, Kimberly-Clark produces these products, the American company which makes Kotex in its native land. The company apparently felt that the less prudish British and French could accept the bright colors and humor more than Americans could. This is also the same brand that shows nude women in German advertising. This ad is from October 1990.