User Defined Keywords

As you may know, syntax coloring feature of Developer Studio supports custom keywords. You should add additional keywords defined for entity sources ('.es' files) and specific types and classes defined in Serious Engine.
Entire list of the entity source keywords together with engine standard types is in the supplied Usertype.dat file. Just append it to the file 'UserType.dat' in the 'Common\MSDev98\Bin\' directory in the installation of Developer Studio.
Remember to restart Developer Studio after you do that.

Auto Expansion in Debugger

Developer Studio also supports automatic formatting of watched variables of some user type. To enable that for Serious Engine types, use the supplied Autoexp.dat file which you can put instead of the original in the 'Common\MSDev98\Bin\' directory in the installation of Developer Studio. If you have already added some of your own formatting there, you should manually merge the supplied file with yours.
Remember to restart Developer Studio after you do that.

Enabling Syntax Coloring for '.es' files

If you have never worked on entities before, you Developer Studio is not customized for proper display of '.es' files, and they will appear all as black-on-white, like ordinary text files, unlike C++ '.cpp' sources which have syntax coloring.
To make Developer Studio recognize your '.es' files as it does with '.cpp' files and do syntax coloring for them, you should use Registry Editor to edit the following key:

HKEY_CURRENT_USER\Software\Microsoft\Devstudio\6.0\Text Editor\Tabs/Language Settings\C/C++

and add 'es' to the list of extensions.
You can use the supplied registry file SyntaxColoring.reg which will do that for you.
IMPORTANT: Make sure that Developer Studio is not running when you do that! If it is, it will delete your settings when it exits.