The callout CSS from Bootstrap doc page

bootstrap-callout.css

.bs-callout {
  border-left: 3px solid #eee;
  margin: 20px 0;
  padding: 20px;
}
.bs-callout h4 {
  margin-bottom: 5px;
  margin-top: 0;
}
.bs-callout p:last-child {
  margin-bottom: 0;
}
.bs-callout code {
  background-color: #fff;
  border-radius: 3px;
}
.bs-callout-danger {
  background-color: #fdf7f7;
  border-color: #d9534f;
}
.bs-callout-danger h4 {
  color: #d9534f;
}
.bs-callout-warning {
  background-color: #fcf8f2;
  border-color: #f0ad4e;
}
.bs-callout-warning h4 {
  color: #f0ad4e;
}
.bs-callout-info {
  background-color: #f4f8fa;
  border-color: #5bc0de;
}
.bs-callout-info h4 {
  color: #5bc0de;
}