After the Prepress Portal 9.1.1 upgrade, the default light source that that will be used is D50. If you want to use a different light source, you will have to adjust the global settings. When surfaces are pre-rendered for PressProof, the correct light source information is utilized.
Set a default light source to ensure color accurate surfaces in PressProof.
This is a global setting. The light source you select here will be used by default by the entire PressProof system. You can, however, apply a different light source to specific jobs or surfaces. For more information, see the PressProof System Administration Guides in Partner Place.