1. Bring the mosaic dataset to ArcMap, and pick the correct renderer, the on the upper right of the symbology page, save it as a function template
2. Publish the mosaic dataset as an image service, in service editor, use the function tab and provide this function template
3. Invoke the function in your client viewer. When performing identify, do not use rendering rule so you can get original values.
For the single uniform block color it is posisble that the source rasters in the mosaic dataset are not accessible by the arcsoc account.