Not where I can look at it just now, but I would add an additional white layer, or your white will have a gray tint.
Edit: There may be an option to just print it twice been a while since I've done white on Black
Someone asked me to expand on this and that alert seems to have dropped off. If you look in the Post "Basic Workflow for Pedal Building" in step four it's demonstrated.
I think his courses are great starting points for beginners and he is very supportive of the DIY community! Even suggesting building a clone of one of his pedal designs. Unlike many pedal designers he recognizes the DIY community is not a threat to his livelihood.