If you get tired of painting, you could insert a layer change filament swap (M600 gcode, or manual option in Slic3r) to swap from black to white as you reach the notch cutout, and back to black once you clear it. You should then be able to see the white color from the front.

Cool idea! I haven’t tried any filament swaps yet but it sounds like it would work well for this. I’ll look into it for a second version.

That's a lovely little end to end tutorial of all the steps of producing a custom part with a 3d printer! ... I've worked in 3d printing technologies for close to a decade so I've read a lot of blogs and articles.

Thanks a lot! I’m fairly new to it so I’m glad you enjoyed it.

Fun . And appreciate you sharing the file.