boostrap 4 css colors code example
Example 1: bootstrap text color
.text-primary
.text-secondary
.text-success
.text-danger
.text-warning
.text-info
.text-light
.text-dark
.text-muted
.text-white
Example 2: bootstrap background
.bg-primary
.bg-secondary
.bg-success
.bg-danger
.bg-warning
.bg-info
.bg-light
.bg-dark
.bg-white