youtube new design uses the windows theme colours for button text but the buttons are forced to a light grey colour causing a visibility problem with darker themes that naturally will have light colours for text and apparently their coke-sniffing devs didn't think of that.

the css forces a black text colour for the buttons.
use the css if you're having problems reading the text due to your dark theme.

paste code below in your usercontent.css or create new style with it for your stylish extension

live"><sub>@namespace url(http://www.w3.org/1999/xhtml);

@-moz-document url-prefix(http://www.youtube.com)
{
.yt-uix-button{ color: #000000 !important; }

}</sub>

before:



after