Html code related queries

Can we write code to change the color of the tab of the website I mean the area where the url is there can we change it then what is the code

No, you cannot apply any styles to page title. But I think you can make a blink to the title tab which I don’t know much about. But there is a way for customizing the theme of the tab. This method is not a code based, you can just change theme of your browser. This will not affect on the other devices when you open the same file. Just adding theme extensions too your browser can change the theme!!

In an Android Lollipop device, the color of the address bar of Chrome (from version 39) can be changed by using Google Tag Manager.
Simply add this meta-tag to the page:

<meta name="theme-color" content="#color-code">

Whereas this is not possible for a desktop, but you can check out this link for a variety of chrome themes.