Turn off background color for SQL strings in PHP Storm

Go to File -> Settings and then to Editor -> Colors & Fonts -> General. Click 'Injected language fragment' and simply untick the Background checkbox.

when sql dialect is not configured, sql strings glow in a annoying yellow. You have to set sql dialect for the file or project.

Go to File/Settings/Languages & Frameworks/SQL Dialects and then select your desired dialect. If you choose the root folder, you will be asked if you want to apply it to all files.

After that you can set the color for injected language fragment as explained by @chocochaos

2 possible colors :

• #52503A (gold/dark yellow) : color code for "Warning" because no Database is set. Go to View/Tool Windows/Database. Then click the "+" button to add a database and click many buttons up to the end.
• #364135 (khaki/green) : color code for "Injected language fragment". Go to Settings/Editor/Colors & Fonts/General/Injected language fragment and change background color.
  For instance you can set a slightly darker color from the original background for PHP. For Darcula theme base, I used #1A1C1C as a darker color.

There may be more cases but these are the two I encoutered.

In my case it was Editor > Inspections > SQL > No data sources configured. To find out what PhpStorm is warning about, you can click on the highlighted area and then on the hovering lightbulb to get the tooltip.