I use Matcha-sea and the Papirus-Maia icon theme on Manjaro XFCE, and I have noticed that since a few weeks the icon of the audio in the pop up notification (which opens when you raise/lower volume) is (very) light gray, and it can barely be seen... in particular, it can barely be distinguished whether volume is on or muted, which is particularly annoying. Other icons in pop up notifications (like the brightness one) are OK.
I attach some screenshots.
This is the pop up notification for volume when speakers are muted:
This is the pop up notification for volume when speakers are not muted:
As I said, you struggle to see the difference.
The pop up notification for brightness is ok instead:
The volume icon when speakers are on should be of the same colour of the brightness icon. And it used to be like that.