Cannot change the color of this block in forums (CSS)

I've been working on recoloring a theme.

I have on IPB I've been changing everything from white to a grey, but this one part.

Gyazo attached with a sample of a post where the white is below the userblock. How can I possibly change this to match the post block?

https://gyazo.com/dfd7be2cbfd0bed5fa7544dbdb33ec78

if you are using chrome

1. right-click the white area
2. click inspect element
3. go to the elements tab if you are not there yet
4. look to the right side of that window
5. figure out where its being colored white
6. click the link on top right of the selector
7. voila.. you see the line of css in your css file that you need to change

you may want to check out this: https://developers.google.com/web/tools/chrome-devtools/

opera has the same functionality since its built on top of chromium.

firefox has something similar but google it yourself.

IE.. don't even think about it.