Also, there can apparently be an obscene meaning attached to a blue heart ...
#1 Blue heart. Blue emoji hearts can be used for a variety of emotions and meanings. On one hand, they symbolize a deep attraction. Think deep waters, mysterious oceans, and stability.
They can be meant as a way of expressing unfathomable depths for someone who feels a meaningful connection.
On the other hand, they also symbolize something much filthier. People use blue emoji hearts to express enjoyment in sexual water sports, as well as indicating a fetish for BDSM. Be aware of the double meaning of this one and attentive to the context that you use them in, so that people know what your intent is!
Sauce: https://www.lovepanky.com/flirting-flings/get-flirty/colorful-heart-emojis-meaning