You can see the accordions and tabs on my test site.
At present I use the default colours for the accordion/tab headers. I would like to change them to the colours that I used with my plug-in which is no longer supported. I realise that I could set them for each individual accordion but, to give more flexibility, I would prefer to define the colours just once – in my child theme. I am not sure which classes (accordions-head, accordions-tab-head etc) I should refer to in the CSS.