Yeah, the default texture that V4 loads with has that purple "bikini"-- but look in your Pose library under "DAZ's Victoria 4" and under that, look in "Materials Sample-Res" and you'll see a MAT Pose called "!All_Natural_NG." Double-click on that, and it will get rid of the purple bikini.

As to the texture maps, you may be looking at the low-res maps that came with V4.  The low-res maps have "Simpl" in the file name.  I believe there is a set of higher-res textures that came with V4. 

Yes, you can change the texture maps to change the make-up-- just remember that you can't redistribute (free or commercially) any texture maps that you change in this manner.  Also, saved your changed maps out under a new name so that you keep both the original and your new version.