Final answer:
If decolorizer is left on too long during Gram-staining, both Gram-positive and Gram-negative organisms will be stained pink. Normally, Gram-positive organisms resist decolorization and are stained purple, whereas Gram-negative organisms do not retain the primary stain and instead pick up the pink safranin counterstain.
Step-by-step explanation:
If the decolorizer is left on too long in the Gram-staining procedure, Gram-positive organisms will erroneously be stained pink instead of their characteristic purple, and Gram-negative organisms will be stained pink as expected. Normally, Gram-positive cells have thick peptidoglycan layers in their cell walls that allow them to retain the crystal violet dye despite the decolorization step and hence appear purple.
However, excessive decolorization can lead to the unintended loss of the crystal violet stain in Gram-positive cells as well, causing them to instead take up the pink counterstain, safranin. In comparison, Gram-negative cells, which have thinner peptidoglycan layers, readily lose the crystal violet dye during decolorization and therefore always appear pink after the safranin counterstain is added.