$re = '/<span style=\\\\?"color:([a-zA-Z\s]*?)\\\\?">((.|\n)*?)<\/span>/';
$str = '<p style=\\"text-align:left\\">
<span style=\\"color:Green\\">
<span style=\\"font-size:12pt\\">
<span style=\\"font-family:Times New Roman\\">There is some content for a mm advertisment.</span>
</span>
</span>
</p>
<p style=\\"text-align:left\\">
<span style=\\"color:Green\\">
<span style=\\"font-size:12pt\\">
<span style=\\"font-family:Times New Roman\\">There is some content for a mm advertisment.There is some content for a mm advertismen</span>
</span>
</span>
<span style=\\"color:Red\\">
<span style=\\"font-size:12pt\\">
<span style=\\"font-family:Times New Roman\\">t.There is s</span>
<span style=\\"font-family:Verdana\\">ome content for a mm advertisment.There is some content for a mm advertisme</span>
</span>
</span>
<span style=\\"color:Green\\">
<span style=\\"font-size:12pt\\">
<span style=\\"font-family:Verdana\\">nt.There is some content for a mm adv</span>
<span style=\\"font-family:Times New Roman\\">ertisment.There is some content for a mm advertisment..</span>
</span>
</span>
</p>
/***************************
String tested in my script
***************************/
<p style=\\"text-align:justify\\">
<span style=\\"font-size:12pt\\">
<span style=\\"color:Green\\">
<span style=\\"font-family:Verdana\\">There is some content for a mm advertisment.There is some co</span>
<span style=\\"font-family:Times New Roman\\">ntent for a mm advertisment</span>
</span>
</span>
</p>';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
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