There is a subtle but noticeable change to the color of fonts in a sticky menu when the page is scrolled and the sticky menu reappears. It looks to be an issue related to antialiasing using grayscale vs subpixel. Before scrolling, the font is rendered using subpixel antialiasing, but when the sticky menu reappears after scrolling greyscale antialiasing is used.
I’ve looked further into this. I now think its browser related. Firefox and older versions of Chrome do not have this issue. Chrome version 75 (Windows 10 64bit) and version 76 do have the issue. The latest version of Edge does have the issue too but I think its based on Chromium code now (like Chrome)… David, if you can’t see the issue maybe you have ultra HD monitors, or are using a different browser than me… Thanks.
Maybe the device itself related with quirks of the browser is causing the issue.
There is one issue that i am aware of if a fixed element ( eg. Sticky Nav ) passed over a transformed element ( could be the slider of example ) that it can mess up certain rendering.
The CSS you provided does change things. What it does is make the font render using greyscale anti-aliasing (instead of subpixel anti-aliasing) before the page is scrolled down. So the font now appears consistent before and after scrolling. The old behaviour, and what I would like, is for subpixel anti-aliasing to be used for both before and after scrolling.