I have been having issues when connecting to HDR desktops (my monitors are also using HDR) from Zoho Assist and I managed to find a solution. Zoho support told me to turn off HDR but that was not an option in our current workflow. 

The issue was that the colours looked all washed off, with no way of telling where an overlaid window ends and the underlying one starts. Also, some buttons, mostly when users were using light themes were hard to distinguish. If you look at the first attachment, there is an Explorer window on top of another program. When the window is inactive, you can't rind the title bar/text. 

I fixed the issue by adding a setting in the Local State file locaed in

I added:

after the first { in the file, right before "os_crypt" (see below).

It now looks like this:

My monitor uses HDR and so does the remote computer. Otherwise, I believe the value should be 1 (sRGB) for standard monitors.

Now, when I log on to the remote computer, the colors are fine. 

I got this idea form this post:

It might useful to have this feature as a setting in Zoho Assist instead of having to go through modifying hidden settings file.

P.S.: you have to restart Zoho Assist once you make the change. Basically it's just a browser window based on Chomium and the settings will only apply when the app is restarted.