How are Bootstrap styles generated using Sass?

[jsphkm]

I downloaded the npm bootstrap package, went into node_modules/bootstrap/dist/css/bootstrap.css, and looked at the styles for .alert-danger:

.alert-danger {
  color: #721c24;
  background-color: #f8d7da;
  border-color: #f5c6cb;
}

When I search those color codes, they do not appear in any other files. Where are these codes being defined/calculated? I’m interested in customizing those values using Sass, and I’m trying to keep specificity overrides as my last resort.

[patrickhlauke]

https://getbootstrap.com/docs/4.5/getting-started/theming/#variable-defaults

https://github.com/twbs/bootstrap/blob/v4-dev/scss/_variables.scss