Using colours to track information

Each node is associated with a particular colour when the grid is defined via the GRID:  command. Colours are used to make it possible to relate shadings representing uncertainty resolutions over nodes with the particular information sources used to remove the uncertainty. Suppose that the colour C (see Table 11.3 for a list of colours possible for different implementations) is associated with the node D, and that an arc leaves D and enters the node B. The effect of the colour is exhibited in three features of the influence diagram:

1. The outline for the node D itself is drawn in its colour C.
2. Any arc leaving the node is drawn in this colour, so the arc from D to B is drawn in colour C.
3. If we adjust B by D, the (possibly partial) resolution in B due to the information source D is shown by shading the appropriate proportion of the outer sector of B in the colour C. This allows us to examine shadings on a node and trace these directly back to the information source.