Change / edit default accordion style (css)

Hello,

i am using the free version of Accordion:

When i create a new accordion, the Style section is set to default values (ex. header: #70b0ff ,  font size: 13px etc...)

i am trying to change these settings so that when i create a new accordion it has my preferred styling by default:

i tried editing the css files but i cant overwrite the #accordion-N# div tags.

can someone help me please?

thanks,

Curly