In this task, we ask you to elaborate the sentence without changing its general meaning. You can do so by explaining further the input sentence, using more precise wording, adding qualifiers and auxiliary information etc.
Q: In certain cases when it is important to understand information very quickly , the visual system may drop the colors , and only work in shades of gray .
A: 
When the need to process visual information as rapidly as possible arises , for example in an emergency situation , the visual system may operate only in shades of gray , with the extra information load in adding color being dropped .