Can I import a specific vssettings file when launching SSMS?
I haven't played with themes, but you can set per-connection properties, including the color of the connection info bar at the bottom of the query tab. And these settings are saved.

If you have a query tab open, go to "Change Connection" (either the button in the button bar, or via the Query menu, top item should be Connection >, and when it pops up the "Connect to a Database Engine" dialog, click on the Options >> button. Go to the Connection Properties tab and the bottom option is Use custom color:. Check the check-box for it and click on the Select... button on the right.

Just use different colors for the different servers/environments.



Technically speaking, there is a means of programmatically interacting with SSMS: write a plug-in / extension. I will list some resources below that deal with this topic. I have not tried it yet myself, but it seems as though it might be a lot of effort for a one-time config update. On the other hand, if SSMS will not record the setting for 100, let alone 400, separate connections (not sure what the limit is), then maybe this would be worth the effort.


The art and science of creating SSMS 2012 add-ins – Part 1 – Laying the Foundation (this is a 3 part series with links to parts 2 and 3 towards the bottom; towards the bottom of part 3 are 6 links to other resources, the first of which I will duplicate as the next item)
How to write own add-in for SSMS 2012 (Final release version)
Automation and Extensibility Reference (for Visual Studio, but it should be very similar with SSMS, at least as of SQL Server 2012)