I see the issue! The selectors need to be more specific. Try this instead:

#bbpress-forums .bbp-forum-title a { 
    color: #6831c1 !important; 
}
#bbpress-forums .bbp-topic-title { 
    font-weight: 700; 
}

The theme CSS has higher specificity, so you need to match or exceed it. The #bbpress-forums container helps with that! 🎯