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Your LimeSurvey version: Community Edition   Version 6.4.1+240108 
Own server or LimeSurvey hosting: Own server
Survey theme/template: LS_lens/Fruity
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I have a multi-lingual survey.
I have a survey with a dark blue background.  I am trying to change the text color of the menu bar (nav-bar) to white.
However, I have not been able to change the text color of the language picker drop-down list.
I have tried many many CSS class (using 'inspect element' from developer tools in a web browser).  

Below please see screen shot.

Has anyone seen same problem?

You need a high specificity for your selector:
 
 

Thanks.  That works.  However, I now run into the next problem.  When I click on that panel, a drop down-list shows up.  However, it is now White on White .  See screen shot.  What would be the classes to change those?  

It works for me. Did you omit the > symbol?