Hi there, welcome to the forum.
Is there any way to change this? Thanks in advance
No, there isn't unfortunately - see the reply below from MusicBee's developer.
As suggested, have a look at changing the fg2 colour instead.
Although its easy enough to switch the font to bold for the current playing line, it can mess with the layout because bold requires more width and hence various calculations need to accommodate the possibility that line breaks change. I dont really have the time to make difficult changes so not planning to add support for this.
Perhaps a standout colour can be used instead
Would appreciate a mod moving this over to the theater mode board in the developers area.