I had an ilestomy for many years and I do remember suffering from colds quite a few times but not to an extent that I believed it was out of the ordinary or a result of the removal of my colon.
I don't use hand sanitisers, I only wash my hands in the morning, and after the use of the bathroom, also after stroking cats, dogs and before to preparing food and eating;
I touch my face, head, hair and other parts of my body without even thinking about it.
I don't do anything out of the ordinary to prevent the spread of germs.