Hey @Numa_Latourte!
The easy answers:
This is probably a regression in the newer viewer of 1.0 
Unfortunately not…
I really don’t remember what was possible in 1.0 re coloured meshes right now. I think it used to be the case that if you provided from gh a bunch of vertex colours the viewer would pick them up, but totally not sure anymore if this was the case.
The example that I posted there has a very strict way of operating, and if you do so chances are it will work:
Basically, for every vertex in your mesh you must have, in a custom attached property, an array of the same length with numerical values. If you select this custom prop in the viewer, it will then assign to each vertex a colour within the blue - pink range.
You don’t need this to be a structural mesh, it can be any mesh!
v = [ x1, y1, z1, x2, y2, z2 ... , xn, yn, zn ]
custom prop = [ v1, v2, v3, ... vn ]
I know this is difficult to achieve in 1.0 and possibly quite cumbersome…