Plot 3D triangle mesh with different colours on front and back side

You can sort-of do this based on the normal vectors with lighting attributes:

fig, ax, p = mesh(
    rand(Point3f0, 30), 
    [3i-j for i in 1:10, j in 0:2], 
    color = :white,
    ambient = Vec3f0(1,0,0),
    diffuse = Vec3f0(-100,0,100)
)

This will give triangles a red color by default (the Vec3f0’s passed act as multiplier to (red, green, blue)), and a blue color if dot(normal, lightdir) become positive and sufficiently large. So a red backside and a blue front side.