Fisherman friend of mine carried a Glock for a time when diving for urchins south of the Farallon Islands outside of the reserve. He got tired of cleaning it, and the sharks are so big he figured it wasn't worth the minor damage the pistol might inflict. Then decided solo diving near all those sharks wasn't worth it either.

Don't some hues of dive suits show up better under water?

yes, hence the term"yum yum yellow" It seems to be particularly attractive to sharks. Not so sure about other colors, including camo blue, which I suspect is a fashion statement.

When I was diving, everyone wore dark blue or black. Although there are sharks aplenty in the waters off the Channel Islands, most diver incidents and fatalities were from other causes (usually failure to observe the diving tables and other standard protocols). I can only recall one shark related fatality - a commercial urchin diver who had been using a surface watercraft in the waters around Point Bennett, San Miguel Island (AKA Shark Park).