The best way would be not to use colour. In fact colour is not necessarily the best way to do it as it relies a lot on good eyesight (which designers usually have, don't forget).
Here are some alternate ideas and ways of emphasising disabled state without using colour - these are suggestions, doing all would probably be overkill and observing users interacting with prototypes would be a good way of assessing different ideas (Hallway Testing is a good thing for this):
Change the hover state. Don't use a
cursor: pointer hover style for example, leave the icon as a standard mouse cursor so nothing happens to it on hovering over the cell. Consider adding an edit icon that appears on hover of an editable cell too. Then a 'not editable' icon could appear on hover of a disabled cell.
Don't style links the links either - if you cells are interactive any text may (or should) have a typical link style. This can be removed, along with any hover state, for the inactive cells.
Consider a tool tip explanation. This would give the user feedback if they attempted to interact (which users will do to find out why). This could be on click, and should be on tap to help with touch screens without hover state.
You could use borders and font weight / style too. These would provide contrast between enabled and disabled. This is a bit like the link styling.
Also, provide a key outside the table, two cells, one styled enabled and one disabled with the works inside to help the user. These could be the point at which you explain why if the reason is common across the table.