Unfortunately, you're not able to change the menu bar colour in Tableau Server.
In the latest upgrade, this colour has disappeared, and the entire menu bar is now a collapsible side panel, so this problem/question should disappear soon. You're able to change the logo and name which appears at the top of your window/tab in terms of customisation, but not the actual colour or font.
Apologies for the non-favourable answer, but I hope this answers your question!
Hi Sankarmagesh Rajan,
I have tried those approaches but it is ging blue background.
one more thing all those workarounds are on the basis of Tableau 9 and 10 versions but we using Tableau 2018.3.
can you please help me out on this.