Screen curtain not black 11.1

I Recently updated my iPhone 6S to 11.1 and a sighted friend told me that my screen curtain is blue not black. Apparently the screen is visible in a dark room. You can not see what is on the screen but it is not completely dark. I have always kept the screen curtain on to save battery life and not disturb others. I can not find a setting to change this back to black. Anyone else having this problem?

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Not black

In older versions it would be gray if invert colors was turned on. I've also noticed that it doesn't completely dim the screen, in a dark room I can see a glow and sometimes the suggestion of things on the screen, but I can't see what it's showing. (Not that I can see the screen that great normally anyway.) The screen turning blue is a new one...is it blue blue, like a bright blue? Perhaps make sure that invert and zoom are off.

I think what iOs still does

I think what iOs still does is that screen lighting isn't turned off, they just display a full screen blackness over the screen. I am suspecting the blue light might come from the lcd backlight. Now I am curious, if it does the same for iPhone X as well.

iPhone X

On iPhone X the screen is completely dark and does not light up.
I like it since it saves on power by not using screen like on other models