I have successfully color some boards with this code:

}
[data-forumid="296"] > div.ipsDataItem_main > .ipsDataItem_title > a {
  color:#ffa500
}

how can i color some sub-categories now?

Just remove the div.ipsDataItem_main > and it should work.

didnt work.

[data-forumid="##"] .ipsDataItem_title > a {
  color:#ffa500
}

Try this instead.

still didnt work

Show me the code you're using for this forum.