Kali is the Hindu goddess often associated with eternal energy, death, time, change, fertility … depending on where Google sends you.

For purposes of this picture she’s mainly depicted as a black person with a lolling tongue. 

Black color - It could mean her all embracing nature; black is where all the colors merge.  Or it might be absence of color, signifying her as the ultimate reality.  ”Color, light, good, bad do not apply to her” (Wikipedia); she is pure everlasting energy. 

Tongue - Kali was being very destructive (killing ppl, whatnot); Shiva lied inert at her feet and Kali, upon seeing Shiva and thinking him dead or worshipping her or something, bit her tongue or stuck it out in shock, which ultimately stopped Kali’s rampage. Fast thinking, Shiva.

Needless to say, she’s still pictured as violent and destructive.  (you go on a few killing sprees and youre BRANDED FOREVER).