You can also change the default startup material without a plugin go into zscripts folder and edit the DefaultZScript.txt to say //startup [pd] [If,1, [IPress,Material: BasicMaterial] ] You can change the text "BasicMaterial" to any material you have installed and it should work with that.
You used to just be able to just save a default material in ZStartups and it'd replace the red wax. I can't seem to find any reference to exactly how to do that online, so maybe that's no longer an option. EDIT: Found it. It's probably the method that MikeZoo mentioned. A little more convoluted than I'd remembered Courtesy…
I use the script way, but you need to match the name exactly and the material needs to be in the startup folder, or it won't be able to find it. Nice with the video :)
I keep forgetting how to update zbrush startup mats when I move computers, so put this together to remember. For some reason I only got the scripts method to work a couple of times. https://www.youtube.com/watch?v=EKMc9JemhVk&feature=youtu.be