calc column and row headers - grid lines and shading have disappeared

[dogface]

Using LibreOffice Calc 5.4.2.2 on Ubuntu 17.10, there are no grid lines or shading on column or row headings. The letters and numbers appear, on a white background. All the other grid lines are fine - but they do not extend to the headings. Does anyone know how to get the grid lines and (usually gray) shading back?
Thanks.

[Donaithnen]

If you ever find out an answer to this I’d love to hear about it. I’m trying to get kind of the opposite effect. I don’t mind the grid lines in the headers, but i really want to get rid of the two-tone shading.

How do I modify column/row header color?

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