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?