I print the buttons with white filament first. After that I change the filament and using Simplify3D I load the labels and set the Z offset value from 11.5mm to zero so the printer starts printing on top of buttons. The smaller the nozzle diameter the better the labels. I suggest you try the one button and com1 label first before printing them all, so you can customize your printer.
Button dimensions: 11 x 6 x 11.5 mm (LxWxH)
Label hight 0.4 mm