Not sure what you mean by "from dos" but if you mean from the CLI/Shell then you can do it this way...
Set the Screenmode to the way you want it using prefs, then copy the and rename the file it creates in ENV:sys/screenmode.prefs to something like, My16ColourPrefs
Then in the CLI/Shell type...
Copy My16ColourPrefs To ENV:sys/screenmode.prefs (return)
This will set the screen mode to whatever your settings were in the file "My16ColourPrefs"
The only problem with this is you will get a requester telling you "Intuition is trying to... blah blah blah)", all you have to do is close the cli/shell window and any others and it will change the screenmode to your new settings...
Not very good but intuition wont be able to set the new mode if a cli/shell window is open to do it properly you really need to make an executable script to this that can be run itself or/and made to close the CLI/Shell automatically...
I'm pretty sure there were some PD utils for doing this if you're not able or wanting to write a script, cant recall the names of them though, try checking out Aminet...
