How to change the accordion toggle style

Hi there,

I am a newbie with Fortuna theme (yet I am seasonal web developer) and found it confusing to find my way as of how to customize things around.
In general: I am lacking “API refference” documentation, e.g. to know all the attributes of the Fortuna tags.

In particular I want to change the color of accordion toggle (+/-) switch, as the reddish color of my theme makes it look like “stop sign”

Thanks