Edit colors in IsleMag theme

Hi all,

I chose the IsleMag theme for it’s attractive lay-out for a news site I am building.

Having gone through the documentation I miss the possibility to change the colors which feature on the home page for the individual posts. The ones in the basic concept are green, yellow, purple and more whereas I like them in more basic colors like black and blue.

I am no good in css but can learn and try.

Can someone give me some advice on how to change these colors?

Here is my website in progress

https://ijsselinfo.nl/

Thank you
Rob