Changing color of NPC messages

Hi.

It’s less for a mod, more for readabillity. Currently the messages of a NPC is white like the most of the other notes. It’s often difficult to recognise the needs of the NPC while reading a book or bashing a zombie.
I browsed a little through the file but with no luck. Does anybody know the line where I am able to change the NPC messages from white to red?

Zhx

In npc::say, in npc.cpp

Could you be more generic?
Which file? Which color code is used?