When your cat has a cold the cat might have a runny nose, sneeze a lot, sniffing, and will have a discharge from it's eyes that is like pus.
Your cat might also develop a cough in rare cases.
There's not too much you can do for your cat when it has a cold but just wait it out and in around a week the cat should be feeling better and the cats cold should go away on it's own without treatment.