They mean here is a heart that is the colour _____. They don't have meaning. I use all the coloured hearts when I'm sending super gay messages to my super gay friends. We send each other rainbow heart messages whenever we're talking about gay shit.
Calendula is a plant. The flower is used to make medicine. Calendula flower is used to prevent muscle spasms, start menstrual periods, and reduce fever. It is also used for treating sore throat and mouth, menstrual cramps, cancer, and stomach and duodenal ulcers. Early research suggests that applying a specific gel (Estromineral Gel, Rottapharm-Madaus) that contains calendula, Lactobacillus sporogenes, isoflavones, and lactic acid to the vagina for 4 weeks reduces symptoms of vaginal atrophy such as vaginal itching, burning, dryness, and pain during intercourse. 2  Leg ulcers.
Calendula grows as an annual/perennial and is an edible flower / herb. Being an annual / perennial plant, it tends to grow either as a single season plant, or a plant that can stay in your garden for many years. Calendula is known for its erect habit and growing to a height of approximately 60.0 cm (1.95 feet). This plant tends to bloom in mid summer. Try planting Calendula if you'd like to attract butterflies and bees to your garden.