There are a lot of silicon filled joints on our motorhome that go discoloured with mould during the winter months. Does not look good and am sure cannot be doing the silicon much good either.
Read an article a year or so back recommending this stuff which i get out every year when we give the motorhome a good spring clean. I squirt a small amount into a spray can cap (or similar) and have an old tooth brush to apply it directly onto the joint. I bit of a scrub and leave it for a couple off minutes then hose pipe out off.
Job done and a big difference. Some are concerned about any chemical reaction with the paint or bodywork – all i can say i have been doing this every year since we have had the van (must be about eight years now) without any adverse reaction. I would recommend you try it on a small patch first.