XPS 8700, S2470L, office app font colors not working

Dell Monitor S2470L connected to (VGA) Dell XPS 8700 has been working fine for over 3 years.  Suddenly the entire display turned yellow. 

• Desktop folders icon color OK.  Background: yellow
• Excel application ribbon display colors but cell and font colors only black,
• Word application ribbon display colors, highlighting OK, but font colors only black
• Microsoft Edge Editor highlighting OK, but text font colors only black

Device Manager, Display adapters:  AMD Radeon R9270: General:  Device is working properly.  Driver: date:  6/27/2017 Ver: 22.19.172.769.  Details:  PCI\VEN_1DD2&DEV_6811&SUBSYS_0BD41DD&  Events: 2/4/2021: Device install requested, Device migrated.

• I have never updated the Device Manager Display adapter
• I do not know what type of graphic card is installed and how to check if there is a problem with it.
• I tried the monitor build-in Diagnostics (never used the buttons before - so did not know what to expect) button:  No change
• I shut down the computer and monitor, disassembled the USB connections (keyboard, mouse, 2 printers, USB upstream port (don't know what it is for - monitor works even if not connected)  and VGA adapter.  Reconnected, restarted.  Display now white instead of yellow. 
• I did not see anything in Event Viewer Application and System log.

I don't know if it is the monitor, the computer, the graphics, card, the connections, display adapter (I have never updated the driver and hesitant to introduce more issues). 

Any other trouble shooting I should try before hauling the computer and monitor to a repair shop?