OptiPlex 7770 - Dell On Screen Display (Dell OSD)

READ THE DISPLAY MANUAL , even any manual for 2 decades covers OSD

OSD is the firmware brain (microcode) in only the MONITOR.

it works by you pushing menu button on just about any monitor for 20 years now. even last CRT monitors had it.

you should really read your manual

in the dell search box, online type the model name of your monitor (sticker on rear Tag tells you that)

and BINGO all you need is there. in the manual.

An OSD is an onscreen menu included with most monitors that allows users to make adjustments to the display. Common OSD settings include brightness, contrast, and color calibration adjustments. Some monitors also include positioning settings and tilt control.

Dell E228WFP, P2210 and 1701FP can be unlocked by holding the MENU or SETTINGS button for 15 seconds.

The other OSD is for software provisioning. OSD is the abbreviation of Operating System Deployment; OSD can be achieved with the help of several deployment tools for ex: BDD 2007, SCCM 2007, MDT 2008 and MDT 2010 Operating System images can be deployed through SCCM using MDT as an imaging deployment server. 

https://forums.ivanti.com/s/article/How-to-troubleshoot-PXE-Boot-OSD-and-Provisioning

https://docs.microsoft.com/en-us/sccm/core/clients/manage/co-management-overview

Yes, you right, but this is apply for Monitors only and not for series OptiPlex 7770 that are desktop computers - monoblocks.  OptiPlex 7770 display have not any buttons for run OST menu (change colors or size for example)  
https://www.dell.com/en-us/work/shop/business-desktops-all-in-one-computer-pcs-for-work/optiplex-7770-all-in-one-desktop/spd/optiplex-7770-aio
There is no information in the instructions as well.

And I think that hardware monitor settings of desktop, can be manage by application. What is the aplpication can be .. I don't know.

Perhaps It can be Dell On Screen Display (Dell OSD) application but no any information or undersanding how Dell On Screen Display (Dell OSD) is working.