CSS Custom Properties

style.css

/* 
Found these unfamiliar `--` prefixes on a page and started researching: https://www.learn-html.org/en/Basic_Elements 
You can prefix a double dash to define custom CSS properties: https://drafts.csswg.org/css-variables/
Browser support is solid: https://caniuse.com/#feat=css-variables
*/
:root {
  --blue: #000;
  --indigo: #6610f2;
  --purple: #6f42c1;
  --pink: #e83e8c;
  --red: #dc3545;
  /* --orange: #fd7e14; */
  /* --yellow: #ffc107; */
  /* --green: #28a745; */
  --teal: #000;
  /* --cyan: #17a2b8; */
  --white: #fff;
  --gray: #6c757d;
  --gray-dark: #343a40;
  --primary: #007bff;
  --secondary: #6c757d;
  --success: #28a745;
  --info: #17a2b8;
  --warning: #ffc107;
  --danger: #000;
  --light: #f8f9fa;
  --dark: #343a40;
  --breakpoint-xs: 0;
  --breakpoint-sm: 576px;
  --breakpoint-md: 768px;
  --breakpoint-lg: 992px;
  --breakpoint-xl: 1200px;
  --font-family-sans-serif: -apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,"Helvetica Neue",Arial,sans-serif,"Apple Color Emoji","Segoe UI Emoji","Segoe UI Symbol";
  --font-family-monospace: SFMono-Regular,Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace;
}