Black

#000000

rgb(0, 0, 0)

hsl(0, 0%, 0%)

.element {
  background-color: #000000;
  color: #000000;
  border: 1px solid #000000;
}

.element {
  background-color: rgb(0, 0, 0);
  color: rgb(0, 0, 0);
}

.element {
  background-color: hsl(0, 0%, 0%);
  color: hsl(0, 0%, 0%);
}

<div style="background-color: #000000; color: white;">
  Content
</div>

element.style.backgroundColor = "#000000";
element.style.color = "#000000";

<div style={{ backgroundColor: "#000000", color: "white" }}>
  Content
</div>