1. A visual reference tag comprising: a core that includes multiple cells arranged to include a center cell and a first layer of cells arranged to surround the center cell; a second layer of cells arranged to surround the core such that the core is centered within the second layer of cells; wherein each cell within the core displays a different color from a set of colors or a gray shade from a set of gray shades, wherein the core includes at least six cells that display colors from the set of colors and includes at least one cell that displays a gray shade to provide a histogram signature detectable by a capture device to locate the core; wherein each cell within the core is nearest neighbors with and abuts against at least two other cells within the core to provide detectable edges between cells of the core; and wherein each cell within the second layer is nearest neighbors with and abuts against at least two other cells of different colors from it and from each other within the second layer and with at least one cell from the core of a different color from it to provide detectable edges between cells of the second layer and between cells of the second layer and cells of the core.