How do you make brown with clay?

Any 2 colors that are compliments to each other (opposite on color wheel) should make a brown or neutral gray-brown...depending on percentage of each color. If you're talking about mixing polymer clay, green + red or blue + orange will probably give best result. Refer to Maggie Maggio's website for color mixing tips (see related links section below).

The question here is vague, and the answer above has some problems. First, any two complementary colors on the color wheel should in theory make black, not brown. People often get this wrong because in practice brown often results due to the fact that it's virtually impossible to find two true complementary colors. Some however come close. I have made a pretty convincing black with a certain orange and a blue combination. When this was mixed with white, the gray produced showed no hint of any color.

Now as to the exact question above. It sounds like you want to make the color brown using clay. Clay comes in a variety of colors. Clay with iron in it is reddish brown naturally. You could take this and thin it down with water to get a brown soup. You could also dry the clay and grind it to brown powder. This could be mixed with any medium to make it brown.