I think Dolphin and Discover share the "Blue square" base design, while Settings and Konsole share the "Black square" one... I usually misclick these app icons because of this.
NOTE: I know Dolphin sticks to whatever the Accent color is set to. But the default color is that shade of blue, similar to Discover.
Would it be possible to change some of these icons? I'm not a designer nor have artistic skills to do so, unfortunately.
Some ideas:
Maybe set Discover to be a paper bag or another shopping icon
Settings could be a gear (wink wink)
Global settings and System settings share the same icon unfortunately. Maybe these could be different :)
I think that you can create a theme inheriting from the theme you choose (breeze in your case) all icons, changing the ones you tell him, so you could just slightly edit the icons you dislike and apply the changing you want, and if the theme comes out nice you can upload it on the kde store and share it!
If all you need to do is to change colors no skill is required, just install inkscape and you're done