It seems like the background color on the panel ‘walls’ are getting clipped. The following works, although it may have some unintended other side effects regarding display outside the display area:
fig = Figure()
ax = Axis3(fig[1, 1];
xypanelcolor = :red,
xzpanelcolor = :red,
yzpanelcolor = :red,
clip = false
)
x = y = range(-5, 5, length=50)
z = [sin(sqrt(x^2 + y^2)) for x in x, y in y]
surface!(ax, x, y, z)
display(fig)
