There appears to be something wrong in the handling of materials using diffuse colours in both FF dev edition (58.0b1) and CC (64.0.3261.0), though it seems to only affect windows (tested in windows 7 on multiple machines).
http://www.babylonjs-playground.com/#LW79KW
Moving across the scene, only one colour (the colour of the first mesh created that is in view) is used across all meshes.
If this was only happening in one of the browsers I wouldn't be too concerned, but that it happens in both makes me a bit wary that there may be some underlying issues. Looking deeper, I think the issue is probably in Angle, as forcing use of opengl in CC with --use-gl=desktop resolves the problems (albeit at a considerably lower frame rate).
There is another (probably also Angle related) issue with transparency (if a mix of opaque and transparent materials are used), which can be seen both in the standard materials demo (with the spheres and grass, the grass texture scaling is off until the opaque spheres are not in view), here (where changing both spheres to be transparent works, but having just one makes both opaque) , and here.
If it is an Angle issue, there may be nothing that can be done this end, (though interestingly I can't seem to reproduce the issues in three.js, though my knowledge there is quite limited).
Edit: Forcing webgl1 also resolves the issues.