Plots > Working with Plots > To Set the Plot Background Color
  
To Set the Plot Background Color
1. In a worksheet, click inside the plot region.
2. On the Plots tab, in the Styles group, click Plot Background and select one of the following options:
Paper Color—Sets the background color of the graph region to the same color as the printed paper.
Transparent—Sets the background color of the graph region to transparent. Gridlines appear behind the graph region.
White—Sets the background color of the graph region to white.