Change Gray color in Modern Guage Chart

Mar 20, 2015 at 6:39 AM
Edited Mar 20, 2015 at 6:43 AM
I tried to change the gray color of the guage chart by trying through styling the ChartArea, but I can't get it to work. I could not found any code for setting the default color. I found only the setting of color for plotted area.
Thanks for any help!