$re = '/([A-Z0-9])(?:([A-Z0-9\.\-\s]*)*\:+)/m';
$str = 'MR. SMITH:
- CAPTAIN AMERICA:
ANT-MAN:
2014 NEBULA:
-2012 IRON MAN:
BOY 1:
1
00:00:07,174 --> 00:00:09,837
BARTON: Okay, hold on.
16
00:00:36,411 --> 00:00:37,527
- COOPER: Nice!
- LAURA: Nice throw, kiddo.
';
$subst = "\<font color\=\"\#FFA500\"\>\<b\>$0\<\/b\>\<\/font\>";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php