.dat Editing

So I've been trying to get back into dat modding, and recently trying to change the colors of some effects. When I try to do it with gimp and GC3 it doesn't come out as smooth as the original. So I was going to try to do it with a hex editor. Basically my question is, is there a way that I can search the .dat file for colors through a hex editor, or are there any tips for finding them? I know the general location of it, but I'm not sure how to pinpoint the actual codes.

You can try here.

Caarrie's FFXI Dats.