In template extra.less
e.g. to change title of category id4
Code:
.block--category4 h2 a
{color:green}
(to get the id number of a category look in ACP > Forums > Nodes open the category settings and look in the browser address bar)
NB: note that for more extensive category (or node) cold changes, create a child theme with those colours and choose that theme in the specific node settings:
View attachment 312340