Cannot select App State variable in Fill color condition

I have a table in which I am loading data fetched using API.

The data gets loaded in table and everything is working fine. I have placed a Button in one of the column of the table.

I want to set the color of that button based on the string value in the field. To set the color I am variables defined in App State.

But when I try to assign any app state variable all the variables show as cannot be selected. That is in red.