[style]: Adding different navbar colours in light and dark modes.

[Arghya-Chakraborty0812]

What's the style idea?

We need to improve the color of the navbar in light and dark modes. It is same in both the modes.

Add screenshots

https://github.com/user-attachments/assets/6c17ef24-db26-4a26-98ab-07655033426f

Code of Conduct

• [X] I agree to follow this project's Code of Conduct
• [X] I have read the Contributing Guidelines
• [X] I agree to follow this project's Code of Conduct
• [X] I'm a GSSoC'24 contributor
• [X] I want to work on this issue

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