Nikon D500 - Manual (Page 130)

130 Menu Guide
If Auto (AUTO) is selected, the color of the lettering in the
information display will automatically change from black to
white or white to black to maintain contrast with the
background. To always use the same color lettering, select
Manual and choose Dark on light (B; black lettering) or Light
on dark (W; white lettering). Monitor brightness will
automatically be adjusted for maximum contrast with the
selected text color.
Information Display
G button
➜ B setup menu
Dark on light Light on dark