When browsing images quickly and then clicking outside the image to close the "preview", the browser text highlight is triggered which highlights the preview image causing it to appear blue. This can be frustrating to get rid of as you have to click somewhere to remove the "highlight", which depending on where you click, will close the preview again.
It seems like the double click is triggering the browser's "double click to highlight text" feature, as when you double click on a word. The area outside the image preview or the next button somehow registers as text meaning that a double click causing weird highlighting.
This video shows one case where it happens, but I also get it at other seemingly random times when I wouldn't expect it. It is very frustrating.
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