crystal violet will unspecifically stain proteins at the concentrations usually used. Therefore you will assess protein contents in the wells, which is not the ideal choice for viability assessments, as secreted (adhesion) proteins may remain in the wells even after the cells have died. Functional viability assays don't have that particular drawback (but possibly others...) while not being much more elaborate. Maybe take a look at neutral red retention or MTT assays for assessment of lysosome potentials or cellular respiration, respectively.
Dear Farin, would you mind to inform us of the staining method you want to/intend to use (guessing it will be done on cell cultures. Thank you, BR and wishes, WM.