SUNTraceEvaluate is an option for SUNTrace, SUNSimplify and some other functions. If set to False, color traces remain unevaluated. Automatic implies evaluation of traces with 2 or 3 color matrices. Setting this option to True will force every trace to be evaluated. For more details, see the documentation for SUNTrace and SUNSimplify.
Overview, SUNSimplify, SUNTrace