If it bothers you, black permanent marker usually is enough to cover it up (just make sure it dries before sliding a Joy-Con into it!).
For Nintendo Switch Console OEM Replacement Housing Screws Full Set
Replacement Nintendo Switch Console & Joy-Con Slider/Slide Rail & Other Parts
Replacement Nintendo Switch Console Joy-Con Slider/Slide Rail And Parts
New Replacement M92T36 Power Management IC Chip for Nintendo Switch Console