Dear rlfwls1012,
That information is stored in the Revit material.
The materials in the Revit project are normal database elements and are thus referred to within the model by their element id.
Here is a sample discussing how to access the material of a ramp:
http://thebuildingcoder.typepad.com/blog/2013/04/accesssing-and-filtering-by-ramp-material.html
Some of the material information is stored in assets.
Here is a discussion from 2013 about accessing these assets:
http://thebuildingcoder.typepad.com/blog/2013/01/read-material-asset-parameter.html
This older discussion on the same topic may now not apply completely any longer:
http://thebuildingcoder.typepad.com/blog/2011/01/material-assets-and-fbx.html
I hope this helps.
Best regards,
Jeremy
thank you