Why don't LCD printers use subpixels in color panels?
If what Thomas Sanladerer states is correct, the Mars 2 Pro (monochrome LCD, no color filter) has a layer time approximately 1/3 as long as the Mars/Pro printers (where color LCDs are used):

                
            
This would indicate that the light passing through the LCD, when the color filter is present, is 1/3. Put it in other words, only ONE subpixel is capable of transmitting UV light.
Consequently, using all of them would not improve resolution because the other subpixels are always opaque.