Interesting observation during a recent interruption to my Internet service. On some of my brighter background Dashboard tiles I had changed the icon color to black. But during a recent interruption in my Internet service and forced to connected directly to my C8 pro running on the x.134 firmware, all the icons which were supposed to be black were white. In advanced settings in the Json file they were still specified to be black. There is no css for them. Later then the Internet service was restored the icons were black again. Curious oddity.
Mildly comical options for comments aside.... And without inspecting the page source line-by-line, the best I could think of would be that the darker icons are source from the Internet whereas the defaults are stored locally... Just a guess....
Probably not the worst situation to arise from an Internet outage, but would also not be the biggest piece of work (I would think) to make the icons available locally, if that is the issue.