Siliconed round windows before repainting jambs - should have done it after?
If you're okay with spending some more money to avoid labor then you can buy a shellac primer to paint over the silicone and then apply regular paint. Before painting clean the silicone with denatured alcohol for best adhesion. It is said that oil-based paints will stick to silicone as well.
If not then scrape off the new silicone and apply paintable silicone or the cheaper painter's caulk.