Visual difference between desktop and service for dropdown slicer selection border

Hi BIanon,

Thank you for your update.

As per my understanding, Power BI currently does not provide a direct setting to modify the border colour specifically around the selected value area of a dropdown slicer. The available border settings apply either to the entire visual or to the dropdown items after expansion, but not to the selection area itself.

Given this limitation, we kindly request you to submit feedback to Microsoft. Since this specific customisation is not available, your feedback can help highlight the requirement for this feature. You may submit your suggestion through the Power BI Ideas platform: 
Fabric Ideas - Microsoft Fabric Community

Additionally, for immediate assistance, we request you to contact the Microsoft Support team by raising a ticket through the link provided below. They will be able to offer insights specific to your account and potential resolutions:
Microsoft Fabric Support and Status | Microsoft Fabric

If you find our response helpful, we would appreciate it if you could mark it as the accepted solution and provide kudos. This will assist other community members encountering similar queries.

Thank you.