Hi, here's an other answer by Michael Lau from Redlands:
( thanks Michael )
Currently TIN layers are exported as green and non-transparent by the �??Export to 3D Web Scene�?� geoprocessing tool. TIN layer symbology is not supported, and the patch does not fix this limitation. The user�??s issue from forum posting below can be worked around by first converting the TIN to a 3D polygon feature class.
In ArcScene 10.2 updated with patch*: 1. From ArcToolbox navigate to and open the �??TIN Triangle�?� GP tool from the 3D Analyst Tools>Conversion>From TIN toolset. 2. Input the TIN and run the �??TIN Triangle�?� GP tool with default settings. 3. The output 3D polygon feature class is automatically added to the scene document. 4. Set the layer color on the new 3D polygon layer in the TOC by clicking on the layer�??s color chip. 5. Set layer transparency on the layer from the layer properties menu.(right click on layer to open menu) (see attached image) 6. Remove any extra layers from ArcScene including the original TIN 7. Export to web scene