Triple mats may seem excessive at first sight but, for a special image that you want to make the most of, they can be worth the effort. However the amount of work involved obviously increases with the number of layers, and it becomes increasing important to work extremely accurately. Small errors are all too apparent when narrow channels of contrasting colours are laid side by side.
Colours for the three layers must be carefully chosen. One effective combination results from placing a contrasting colour between two mats of the same or very similar colours.