Interesting. When I switch a plot from 'Shaded with Edges' to 'Hidden Lines Removed' by Simulation symbols get brighter, but the plot does not get brighter.
Changing the 'Ambient' lighting value from the default of .3 up to something like .7 makes the plot (and sim symbols) brighter, like you show in your example picture.
I often crank the 'Ambient' lighting up a bit in normal parts and assemblies. The default value always produces rather dim graphics and images.
Definitely both the symbol and the part with results will be brighter.
i have seen the image attached by you, even in that both looks brighter..