Protein samples boiled in buffer are blue in color and turn blue-violet after being left at -80°C. What is the reason for this? Does it affect the subsequent electrophoresis?

Protein samples boiled in buffer are blue in color and turn blue-violet after being left at -80°C. What is the reason for this? Does it affect the subsequent electrophoresis?

Bromophenol blue will change from yellow to blue-violet with the change of pH value, which does not affect the normal use of the product, and the occurrence of similar discoloration does not affect the subsequent electrophoresis, and the experiment can be continued.