The issue with the precise colors are very hard to quantify in general, because there is no universally accepted notion of how a given RGB color should look like. There are various attempts to improve but I think none that can take all parameters into account. For instance, how colors look like on your screen will likely depend on the external lights, whereas in the headset they typically don’t because the headset is a mask. Moreover, both Sketchup and VR Sketch don’t display walls by just applying the RGB value. If they did that, then you would see nothing. For example, assuming you turn off the edge display, then in a room with the same white material on all walls and ceiling and floor, you would only see a completely white screen. That’s why the color is made a bit darker depending on the angle. Moreover, in some configuration (e.g. on PC in the warehouse in “quality” display mode) then the computations are more advanced, e.g. the light reflected from the warehouse’s brown floor appears on downward-facing faces of your model. (In older versions of VR Sketch, there was a bug that made this pink-brown hue still appear even after you are out of the warehouse, giving a pink-brown tint to all your ceilings; this is fixed in recent versions.)
We can look into a precise example if you have one: please give us a small model and tell us exactly which hardware you are using, and which face of your model we should check for being quite different in Sketchup and in VR Sketch.