You can find the declaration in: `/templates/ja_athena/css/template.css'
.bg-primary {
background-color: var(--color-primary) !important;
}
.bg-secondary {
background-color: var(--color-secondary) !important;
}
.bg-success {
background-color: var(--color-success) !important;
}
.bg-info {
background-color: var(--color-info) !important;
}
.bg-warning {
background-color: var(--color-warning) !important;
}
.bg-danger {
background-color: var(--color-danger) !important;
}
.bg-light {
background-color: var(--color-light) !important;
}
These classes are set with variables which takes background color from the Theme Color in template, you can override background for these classes or change the theme color as you wish.