Silicone or Caulk

I've been told that silicone shouldn't be used because it turns black in the southern climates, sun, and air pollution...
When removing a number of the portlights, I discovered this black ewy gooey stuff... I wonder if that's what happens to silicone... I think I'm going to stick to Lifecaulk or 3M 4200, depending on the situation of course ;)
So there sit the portlights on the bench, holes in the boat where these once were, while the radio forecasts thunderstorms with 40 mph winds...
such has been life trying to work on the boat during SWFL's wonderful rainy season... not to mention the boat doesn't have AC and the weather has been in the low 90's. I'm getting use to the heat and humidity. I just wish it wasn't rainy season, it's making it really difficult to get the much needed work done before move-on date in just four days now...