Also see the official documentation
Convey meaning through color with a handful of color utility classes. Includes support for styling links with hover states, too.
Contextual text classes also work well on anchors with the provided hover and focus states. Note that the .text-white and .text-muted class has no additional link styling beyond underline.
.text-primary
.text-secondary
.text-success
.text-danger
.text-warning
.text-dark
.text-body
.text-muted
.text-white
.text-black-50
.text-white-50
Similar to the contextual text color classes, easily set the background of an element to any contextual class. Anchor components will darken on hover, just like the text classes. Background utilities do not set color, so in some cases you’ll want to use .text-* utilities.
Guideline