They are general purpose. They are a translucent oil paint (actually ink... I think). They are used to touch up photos. You know those black and white photos with a little color (perhaps coloring a flower pink)? That is what they are used for. I've used them on figures with great success, but I was thinking of maybe using them on my jets and AFV's for shading purposes. They blend nicely and can be applied with a Q-tip. Here they are:
http://www.dickblick.com/zz004/26/