Hello!
Ok, it starts to look better:
EDIT: updated:
EDIT: added git hub repo
(requires node 16)
Source will be available after I crack the problem the Reflection block producing an error in NME when I am using it with a environment texture. And I want to add more shine to the diamond and better lighting.
Click on the left bottom bug icon to open the Inspector. Select the Big Diamond or the Small ones:
Then choose matDiamondxx to change the color.
More advanced users, use directly the node material inputs:
Part #4 under construction 
R.