What I thought was black was a dark umber. It was working with the other paintings but now trying to do rocks, I mean rocks are not brown. I mixed in some purple and got it to work - then I ordered some black paint.

I've been watching videos on color theory. It's far more complex than I'd like it to be but its more science than art. I'm pretty comfortable with science so I have every confidence that I'll figure it out. 

I ran across a video that it way over my head but I needed something to watch while I was on the rowing machine. He talked about how they always tell you not to use black. The one art seminar I went to they said the same thing. It was all about mixing your own black. The woman running my seminar went into how using the paint out of the tube makes you look like an amateur. It seemed like an odd thing to say to someone who has never done any painting before. I have been having a lot of fun mixing the colors and getting what I want. I don't see any reason not to start with say a green tube and then mixing a bit from there. I haven't really explored the other colors in my kit yet. I was going to get to that when I get through these beginning paintings. 

In the video the guy mixed black and yellow and ended up with green. He was illustrating why it doesn't always work to use black to darken a color. I'm unclear what sorcery is at play here but I'm going with it being akin to a hidden pigment.