How can change the color behind bubble

Hello, i can change the buble color after much work reading this forum, I created a child theme. And the end my bubles are white.

Now my problem is the color behind, i dont know extactly the name, (perhaps “content”) I have installed firebug, but i dont know how can change this color.

The background i know how I can change.

Other question is if i can change the color backgroun of bottoms, becouse
i do this in settings theme and dont work,

Thanked you