I have many tables, actually data grids, where most of the cells will be editable, but some may not depending on the users permissions. I am thinking of using light gray backgrounds on the read-only cells.
Since this topic has recent activity I thought I'd give an update. We considered many of the suggested option and went with simple light grey background. User interviews discovered this solution to be quite intuitive to our audience.
- Adding icons, even subtle ones, added a great amount of visual complexity.
- Graying the text made it more difficult to read and seems to indicate text that is in some state of transition.
- Adding an indent to indicate editable cell is not possible as that is what we use to indicate focus.