Do you experience problems during downloading?
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This is a pretty common issue with Dark Mode in Yosemite, look at Dropbox, for instance. If you use the monochrome icon instead it's all black. This should be resolved before Yosemite ships in the fall.
Just wondering if there is any possibility of this bug getting fixed soon. Sabnzbd icon in the menubar completely disappears when using dark mode in Yosemite