Magento 2 + PhpStorm 2017.2.3 InstallData.php file icon is displaying as a notepad icon instead of the blue icon

You can see the image below. Only when I create InstallData.php file, it becomes like that. Please anyone knows why this happens? Thanks in advance.

This Only occurs on InstallData.php files:

grey letters

This is the normal way how a file should be like:

colorful letters