Are other colors for the headscarf permissible in Sharia, and is wearing black more rewarding?

The Sharia-compliant hijab does not require a specific color. A woman may wear any color she wishes, as long as the hijab fulfills the Sharia conditions: that it covers the 'awrah, does not resemble men's clothing, is not tight revealing the body's contours, is not transparent showing what is beneath it, and is not a cause of temptation. And it is not the case that because black is not specified or recommended, it is therefore recommended to change it. Rather, the matter is equal in this regard and refers to personal preference. It is advised not to overthink such trivial matters.