By pressing the button, the "Choose The Color" dialog appears. Here you can set the color of the bar chart. You have five possibilities for set this color: Swatches, HSV, HSL, RGB or CMYK (see the figures below).
The sizes used for the bar chart are: "Small" or "Large". By default the size used is "Small". In the figure below you can see how can you change this option.
In the following pictures you can see how a "Small" or a "Large" sized bar chart is:
"Ok" button - this will change the previous setting with the actual settings
"Cancel" button - the change in setting will be ignored