Styling tab header in accordion

I am testing my upgrade to Accordions 2.1.18 under WP 5.3.2 and Tempera theme.
Following tests use Firefox as browser.
The styling looks OK for the accordion, as here
https://test.pat.gen.nz/accordion-clubs/
When displaying the same accordion as a tab, I cannot get the active text to display as black (rather than white), as here
https://test.pat.gen.nz/tabs/

There is an additional problem when displaying under IE.
Again the accordion is OK but, when displaying as a tab, the inactive header is a pale colour (not #bcd2ee as expected).
Andy