JavaScript variable color in JetBrains WebStorm

The colours for those member fields are different because they are different types.

The fields coloured purple are object variables and the fields in light orange are function variables.

IntelliJ (or WebStorm) has determined this by examining the export field of the targeted JavaScript files.

See screenshots below:

Open Settings/Preferences dialog, and under the File node, click Colors & Fonts and select JavaScript. From right panel you can change all the colors

It’s important to note that the check box Use inherited attributes is selected!

For more detail go to this link