Well the most easy way to change NPC name color is this way.
1-> Make an backup on ur npcname-e.dat
2->l2encdec.exe -s npcname-e.dat
3->delete old npcname-e.dat and rename dec-npcname-e.dat to npcname-e.dat
4-> open npcname-e.dat with L2ClientDat_en and press decode
5->now u will have npcname-e.txt look for ur npc in it and on color change to quest
6->open L2ClientDat-en and press encode
7->l2endec -h 413 npcname-e.dat
8->rename it to npcname-e.dat and that is it you now have changed npc name color
This require that u have l2endec and l2ClientDat and u put that npcname-e.dat in same folder as those program and when u run l2encdec u will have to run it from dospromt aka cmd and on dospromt u will have to make is like this ex "c: cd c:urfilemapname where u have ur l2encdec.
I will send u a link where u can download my version of those 2 programs.
http://www.2shared.com/file/tohu4b_D/l2encdec.html
Hope this will help u.
//dreambot