I apologize if you took my reply as being condescending as I meant no disrespect. From lassis attachment I can clearly see how the paper shadow blends in with the new lighter background color. I never did like the way the ps layout looks with the shadow on so in the options I turn off the paper shadow. This way there are only two colors, the paper and the background. I would recommend you doing the same and see it helps.
The only other option is turning off the paper background as previously suggested, unless of course you have the ability to hack the program and modify the code to change the color.
Happy Civil 3D'ing
🙂
ACADuser
Civil 3D 2018, Raster Design 2018
Windows 7 Enterprise
Dell Precision 5810 Workstation
Intel Xeon E5-1630 v3 @ 3.70GHz
32GB RAM, NVIDIA Quadro K2200 4 GB GDDR5
DUAL 27" Dell UltraSharp U2713HM