Maybe I phrased it weirdly. The icons look like this:
Do you notice how much brighter they are in the minimap screenshot I posted? They look like they're semi-transparent.
But in motion, this looks less like transparency and more like flickering. Like the icons are being turned on and off at high speeds. Unfortunately, my screen recording tool doesn't capture it properly, it just looks like in the screenshot.
I think you should be able to easily reproduce this, since I didn't change that many of the default settings.