Identify your different instances query windows with different color codes.

If you work/connect to multiple instances at same time, Its very difficult identify which query window connected which server.Some times it will confuse.(I know in the below it will display server name)
Color coding the status bar in the Query window in SQL Server Management Studio is only available if you are using SQL Server 2008 Management Studio. Although I must note that I've found that using versions prior to 2008 R2 SP1

Ex:
If you are connected to DEV,UAT,PRD instances, and opened 3 query windows.(one query window from each instance), So without moving your mouse cursor to top you cannot tell which window connected to which server.
Note: This color codes only possible with registered servers.I assume you already registered required instances.
I registered 3 instances to my management studio.

In The above image you can see all the three windows has same color.

To color code a connection, you first need to open up the Registered Server view. Under the "Local Server Groups" item of the "Registered Server" view you will be defining your servers and how they will be color coded. Figure 2 shows three of my local instances that I want to color code. Right click and select properties of the registered server.

Now select connection properties window, and select Use custom color and select required color for your instance.

Here I selected Red for DEV, Green for my UAT and Blue for PRD.

Now open one new query window for each instance, see each window has one color.
Here I selected Horizontal tab group view to see all the colors.