One tiny change if you could do.
Could you defined 2 variables: headerClass and accordeonHideAreaClass on line 50 in the var section.
There you can assign those variables to colorScheme + '-a11yAccordeon-header' and to colorScheme + '-a11yAccordeon-area'.

Then reuse those variables on lines: 80,81 and 155

After you do this I will merge your pull request.