This can be done by placing a property node linked to the graph and/or chart.
The specific property node can be accessed by right-clicking the terminal of the graph or chart, and browsing to Create»Property Node»Plot Area»Colors»BG Color.
The specific color can be selected either by wiring in a hexadecimal number with the form RRGGBB or by wiring a color box constant to the property.
For example, the below VI generates a random RGB color and updates the front panel graph's background color every second:
