Love Potion

In Harry Potter and the Half-Blood Prince, the smoke coming out of the love potion changes color to that of whatever Hermione is describing. The final scent that comes out of the potion is orange, as is Ron's hair. That's why Hermione lies saying that she smells “spearmint toothpaste” because she obviously doesn’t want to say “Ron’s hair” out loud. Also, after Harry arrives at the Burrow, Ron pokes Hermione’s lip and says she has toothpaste on it.