Answer:
All the bacteria would appear purple(gram- positive)
Explanation:
Gram stain is used for distinguishing gram-positive and gram-negative bacteria. Gram-positive bacteria appear purple because it does not gets destain after decolorizing step and gram-negative bacteria appears read or pink because it gets decolorized after decolorizing step and then it gets stained by safranin which provides a pink color to gram-negative bacteria.
So if a student forgot the decolorizing step then gram-negative bacteria will not get decolorized and will not take safranin stain so even gram-negative cells will appear violet. Therefore all the bacteria will appear violet or purple(gram-positive).