Arrow customization | Carousel widget

Hello there!

I’ve been struggling for some time now to find a solution to customize the arrows on SO Carousel widget. The website was given down to me to finalize it and I would truly appreciate some help :)

This is the website I’m currently working on: optilab.net
And this is the sister site: optilabanalytics.com

The carousel on both sites is placed under News. So the previous programer managed to change the arrows on Optilabanalytics (the blue arrows) and now I’m suppose to do the same on Optilab except I have a different color – but that doesn’t really matter :)

If I checked correctly, the arrows are part of a font/icon set; so how do I work around with that? Currently I have both arrows uploaded in Media on WP, tried all kind of things so far and nothing seemed to work.

I would truly appreciate any help and advice! Thank you in advance :)

Kind regards,
Lara