Hi jmv,
I can see why that would look strange! The cell isn't actually blocked; instead, the reason you see the x through the cell is because you have no value in that cell. When you color cells by value in a data table, JMP wants to highlight the fact that a particular cell is missing a value. This is important when your color scheme uses white to indicate something (which often happens with gradient color schemes) because it would be ambiguous (especially for a character column) to show a blank cell as white.
I hope this helps!
@julian
![julian_0-1663851350349.png julian_0-1663851350349.png](https://community.jmp.com/t5/image/serverpage/image-id/45690i76CB183D33A3EC7D/image-size/medium?v=v2&px=400)