It might be an overlapping object which is also rendered in the viewer and mixes with the material colour. Can you check that all but the SDDisplay components are switched off for preview in Grasshopper?
Here is the material rendered with the custom environment:
I have scaled the texture within the actual definition.
All colours are displaying significantly darker than their RGB values and
hence are not close to the colour that should be presented.
I can see this being a problem when an end user selects a colour and commits to purchase once we have the definition embedded in a site with your API linked to a retail cart.
I will watch the video, but is there anything else you can suggest. Is the Shapediver material 701 adding colour to the rGB values.
The ShapeDiver material presets are aimed for a simple and quick test rendering of your product. I recommend to use the advanced material which gives you more flexibility to create finish you have in mind.
701 Grey Fabric material preset, as the name suggests, adds grey colour and can make the final material appear darker.
However, if all colours show darker go to model Edit Mode and increase the intensity of the ambient light to brighten up the scene. Make sure to Save Light Scene and Apply Settings when you are done.