Problem: Setting the background color for image services to 'No Color' results in a gray background
If you change the background color of an image service to 'No color' on the symbology tab of the ArcMap Layer Properties dialog box, the background will appear gray.
ArcIMS and ArcGIS define 'No Color' differently.
Solution or Workaround
If you want an image service to have a transparent background:
- Open the image service layer Properties dialog box.
- Click the Advanced tab.
- Check the 'Background transparent' box.