Change theme color

Hi everyone,

I’m rebuilding my website: https://www.g-cg.com
And I chose the twentyeleven theme as i like what they’re doing with banners.

I changed the colors to the night theme but I would like to change the color of the main body where the posts appear over to something a tad lighter.

I have already created a child theme and found where to change the banner color using this code:
#branding { background: #1c1c1c;}

That successfully changed the banner but now I don’t know how to change the rest of it.

Any help would be greatly appreciated as now the two colors clash ??

Best,