Confirmed. I guess this is because the slider is using Unicode symbols rather than real icons. In the battery menu, the symbols make sense because the text is white, so the solid sun is white. System Settings used to use a light-on-dark color scheme, but now uses a dark-on-light one, so the solid sun is black.
Confirmed. I guess this is because the slider is using Unicode symbols rather than real icons. In the battery menu, the symbols make sense because the text is white, so the solid sun is white. System Settings used to use a light-on-dark color scheme, but now uses a dark-on-light one, so the solid sun is black.