Well, it depends....
If the bass is too bright, it can feel thin and clash with other higher-frequency range instruments too much or it can even hurt to listen to.
If the bass is too dark, then it can make the mix muddy or can be not clearly heard on smaller speakers (for example on cell-phones).
And it also depends on the genre and the song emotions, of course.
But as the time goes, I tend to make the bass darker, especially for heavy genres.
For the bass bus processing I always use my ToneSpot Bass Pro plug-in.
May the muse be with You!