What makes art sell???????

I have been on nights for the last two weeks, which has meant my art work coming to a stand still. I have to just try and survive the two weeks and any creativity is gone. On a happier note, I have sold these three paintings at different places over the last month. A great feeling selling your art work because you know somebody really loves it enough to buy and treasure it. They appreciate it bydisplaying it on their walls for family and friends to view. But why do people buy your art and what is a winning formula? I have no idea. Do people buy art because they admire the painting, or is it because the colors suit the room they wish to display it in, or are they reminded of a feeling, an emotion that is captured by the picture? A friend of mine has a theory that only paintings with orange in them sell. After this I went around to art shows checking out the paintings that had sold. Sure enough most of them did have orange in them. All I know is that I will keep painting things because I like them. The subject needs to appeal to me, inspire me and bring out an emotion or a thought. Once art is no longer enjoyable I think there will be no point in continuing to paint.