Which folder directory is this map stored under?
Thanks
/ZData/Textures/Txtr40.PSD
Please note that you should never change, remove from or add to the contents of the ZData directory.
txtr40.psd does not look the same as the one showing up on the normalRGBMat… 
Unless there is some tweaking that I have to do to make it look the same…
Hi
I have uploaded a 256 x 256 texture for use in the NormalRGB material’s texture slot. The green channel is currently set in reverse of the default NormalRGB texture.
The file is in photoshop format so you can invert the channels to your liking. To do so (in photoshop) open the Channels window, select the red, green or blue channel and press Image > Adjustments > Invert ( CTRL + i ). Then just save and apply the texture to the material back in ZBrush.
Remember, any normal map you generate in any program can be tweaked the same way, post creation, by simply inverting color channels.
I added a fourth layer to the Photoshop file. The deault ZBrush NormalRGB texture has blue values from 128 to 255. The fourth layer has blue values from 0 to 255. Depending on your render engine you may be able to use the extra color fidelity.
Mark
I forgot to add:
For some materials you need to perform a Best Render to avoid a seam along the document border, the NormalRGB material is one of them.
Before doing a Best Render set Light > Ambient to 0 and switch off Preferences > Performance > Multi Render. Multi Render causes white speckles when best rendering some materials. If you are using 3.12b I believe Best Render is off by deafult.
After the Best Render press Document > Export.
Hope that helps.
Mark