How to write the correct regular expression in php?

I need to cut all tags like
<span style="background-color:SOME_COLOR">test</span>
and ONLY if style is background-color, not any others. Also, all text inside the tag must be saved. I tried to use something like this, but it doesn`t work

$pattern = '#<span style="background-color:s*[^;]+;">(.*?)</span>#ui';
$result = preg_replace($pattern, '$1', $inputString);```