A few different 'dos for our half-Klingon.
'Do No 1:
The 'Almost There' 'do.
Cut at different levels, a precurser to her eventual bob.
'Do No 2:
The 'Mean Klingon' 'do.
In the episode 'Faces', we see what B'Elanna would have looked like if she were full Klingon. I guess the genes for curly hair come from that side of the family.
'Do No 3:
The 'Bob' 'do.
Once she gets this (in the second season) there's really not that much variation. Well, in comparison to Janeway.
'Do No 4:
The 'It Never Happened' 'do.
Just like Janeway's 'do in 'Parturition', this appears for one episode and is never, ever, mentioned.
'Do No 5:
The 'Wavy' 'do.
Almost everyone (apart from Chakotay) has a fab hairdo in 'The Killing Game'. B'Elanna is no exception.