When styling filter cells, the property “color” does not apply. Basically, setting style_cell={"color": "red"} or style_filter={"color": "red"} doesn’t change the filter text color. Same for border-color (but border does apply).
style_cell={"color": "red"} should work, but please note that style_cell has the least priority in style_* props (the full list is here. If you could share a snippet of your DataTable component definition, it might be easier to say why it isn’t working in your case.
border-color won’t work because Dash expects camel cased CSS properties just like React. So borderColor works instead.
The bug also happens with the code snippet from the documentation [here].
Just add style_cell={"color": "red"} to the DataTable argument. All texts in data cells are colored in red but not for the filter cells.
Oh, I am sorry… I completely ignored what you meant by “filter cell”.
I don’t know if it is a bug or just a design choice. In any case, the cell style does not apply to these cells, as the default style takes precedence. So yeah, it does not work.
I would consider opening an issue in the repository, it might be easier for the maintainers to reply there.
I think it’s a bug since setting style_cell={"background-color": "red"} (or with style_filter) works, which means that this argument affects the filter cells’ style. I opened an issue on GitHub.