Mac IIfx SuperMac Spectrum/24 video to VGA Monitor

I just received a Mac IIfx w/ Supermac Spectrum/24 video card. The computer is running OS 7.6.1. I am connecting it to my trusty old Dell 15" LCD VGA monitor via a Mitsubishi Mac to VGA adapter with 6 dip switches. The video is in color and readable, but washed out. Specifically, it seems like gray colors (like grayed out menu items) simply display as white (so they are invisible in the menu bar). The same applies to the tops of finder windows, which display as white. Also, Mac OS splash screen colors are washed out. Please see attached pics. I've tried:

- all combinations of dip switches

- replaced video cable

- checked Monitors settings (256 colors)

- factory reset my Dell monitor

None of this helps.  Any ideas?