Request to make the top-of-screen black color's parameters user-adjustable (I can't see many of my tabs.)

Below is a screenshot of a section of my tabs. I don’t know why there is such variation in the brightness of different tab icons, but since there is, would it not be possible to make the parameters that determine ‘darkness’ and ‘brightness’ user-adjustable?

Even in the URL line, I find it impossible to edit because I can’t see where I am when I cursor across text. Although the bar can be brightened by clicking in it, as soon as the cursor is moved the brightness disappears. I have to make any alterations to the URL line by copying-&-pasting it into a text editor, fixing the text, and then dropping it back into the URL line. User control would fix that.

Thanks.