It's been a while since I've messed with it.
The class you're looking for is .inner_column.
The profile sections each have a div with the assigned class .inner_column. These sections are profile_header, profile_content, purchased_games, and collections. Collections is further divided into a separate row (class="collection_row") for each collection you display, and there is a child div with class .inner_column within each row.
I meant to do a styling guide at one point, but it ended up on the back-burner, and I just haven't had the time to get back to it.
Here's the custom CSS I'm using on my profile page at the moment:
.game_grid_widget {
text-align: left; !IMPORTANT!
}
.game_thumb {
border: solid #000 1px;
}
.inner_column {
background: #EDD5BE;
border: #271C14 solid;
padding: 50px 50px 30px 50px;
border-radius: 25px;
}
.footer {
background: #333;
border-top: #271C14 solid;
color: #fff;
}
.game_column::before {
content: "My Games";
font-size: 1.5em;
font-family: '04b_03',Lato,LatoExtended,sans-serif;
margin: 0 0 10px 0;
font-weight: bold;
display: block;
}