Change the Tray Icon Color
You can pick from two tray icon colors. A black or white scheme. The client tries to detect which color will fit best to your window environment (if it's light or dark), but it might disappoint and pick the wrong color.
If you have a dark theme and the icon is black, here's how to change it. Open up the Settings and under Apperance, change the Menu bar icon color from Adapt to system to either Black or White: