What colour is a kiss?

Monica loves painting a lot of things in colour: red ladybugs, blue skies, yellow bananas... but she has never painted a kiss. What colour is it? Is it red like a delicious tomato sauce? No, it isn&t, since red is the colour of annoyance... Is it green like the nice crocodiles? No way, because green is the colour of vegetables and she doesn&t like eating them! How could she find out what colour is a kiss?