Disallow hex colors.
a { color: #333 }
/** ↑
* This hex color */
The message
secondary option can accept the arguments of this rule.
The following patterns are considered problems:
a { color: #000; }
a { color: #fff1aa; }
a { color: #123456aa; }
Hex values that are not valid also cause problems:
a { color: #foobar; }
a { color: #0000000000000000; }
The following patterns are not considered problems:
a { color: black; }
a { color: rgb(0, 0, 0); }
a { color: rgba(0, 0, 0, 1); }