When a spend chart lands on a board table, the first mistake is treating every visual as interchangeable. A stacked bar by category shows composition; a Pareto line shows concentration; a bubble chart compares spend against contract coverage. Mixing those questions on one slide creates arguments about formatting instead of sourcing decisions.
We start every engagement by writing the question on the chart margin: 'Where is spend growing faster than volume?' or 'Which suppliers hold more than 15% of a single category?' That single sentence becomes the title. Executives then know what evidence they are supposed to extract.
Colour is restrained on purpose. Brass-toned highlights mark categories under review; charcoal greys carry baseline years. We avoid rainbow palettes that imply ranking where none exists. Legends sit adjacent to the data, not buried below footnotes.
Annotations carry the narrative. A spike in MRO spend might note a plant relocation; a flat IT line might reference a deferred refresh cycle. Without those notes, finance assumes procurement missed a saving that was never in scope.
Finally, we pair every chart with a one-page table of underlying figures. Directors who distrust graphics can reconcile numbers; those who prefer visuals get the story. Both paths lead to the same category map.