Crystalline silicon dioxide -- quartz -- would be very resistant to staining. However, I don't know what "Blue Quartz" is . . . except that it's NOT blue quartz. Quartz (sand or crystals) can come in tan, clear, rose or other colors . . . but not blue. See http://wikipedia.org/wiki/Quartz

So, I have no idea whether your builder's product, trade named "Blue Quartz" is actually more stain resistant than while plaster or not. However, I can tell you that ANY colored finish will make your pool significantly hotter than it would be otherwise. And, that might not be what you want in south Texas!