Solid colors. The solid coloration can come up if both parents carry the solid gene. Even if both do it's not always sure it will show either. I had a very odd statistic in one of my litters where I got THREE solids and ONE spotted! How big are the odds for that?! :)
You can often see the solid cats "markings" which is called ghostmarkings. This is no real markings but it tell you what pattern the cat carry "unerneath" the solid color. All my solid kittens was spotted "in base".