Changing background color of the top area

I did some research, but I did not find a button to change the background color. How can we change the background color of top area?

I’m not quite sure what you mean because the area you have boxed out in the image looks like the mobile OS’ top banner for holding information like the time and icons. To my knowledge, app developers have zero control over the info in there (including BG color) and never have had control over that. I don’t even think the phone’s owner does – or at least I’ve never seen it on my own devices.

Perhaps, that answers your question? Could you be more specific if not?

There was a bug with this area being the wrong color in some 2.4.X builds – but it should be fixed in the latest 2.4.33 and newer, I think.