Please use this CSS code:

#wpforo #wpforo-wrap a:hover{
    background-color: #f21313;
    color: #f21313;
}

thanks for your answers its work for me can you please solve my another problem that is on a screenshot I highlight a up arrow I want to set this color to black how can I do that? please help 

Please follow to this support topic:

https://wpforo.com/community/how-to-and-troubleshooting-2/fa-chevron-icon-styling/#post-12964