How To: Create a colormap index within the attribute table of an integer raster
Instructions provided describe how to create a colormap index within the attribute table of an integer raster.
Create a value attribute table (VAT) for the raster, if it does not already possess a VAT. This can be done using the 'Build Raster Attribute Table' tool in ArcToolbox.
Add three new fields of type double to the raster attribute table, and name them 'Red', 'Green', and 'Blue' respectively.
Start an edit session with the target workspace set to that of the raster.
For each record, enter the desired RGB value in the fields named 'Red', 'Green', and 'Blue' respectively. These values need to be expressed as a percentage of 255, so a value of 50 would be 0.196078 (50/255 = 0.196078).
Stop the editing session and save the edits to preserve the changes.
Remove the raster layer from ArcMap's table of contents, then reload the raster back into ArcMap so the colormap can be recognized.
Right-click on the raster in the table of contents and select Properties > Symbology tab.
The colormap should now be available in the list of rendering options. Select the colormap renderer and click 'OK' to display the raster using the newly created colormap index.