You would have to target each post using the unique ID in the HTML – use inspect element to find the ID of each post.
For example:
.post-1403 .inside-article {
background-color: #1E72BD;
color: #FFFFFF;
}
.post-1403 .inside-article a,
.post-1403 .inside-article a:visited {
color: #FFFFFF;
}
.post-1403 .inside-article a:hover {
color: #EFEFEF;
}
You can also target post formats, like this:
.format-standard .inside-article {
background-color: #1E72BD;
color: #FFFFFF;
}
.format-standard .inside-article a,
.format-standard .inside-article a:visited {
color: #FFFFFF;
}
.format-standard .inside-article a:hover {
color: #EFEFEF;
}
.format-quote .inside-article {
background-color: #181B21;
color: #FFFFFF;
}
.format-quote .inside-article a,
.format-quote .inside-article a:visited {
color: #FFFFFF;
}
.format-quote .inside-article a:hover {
color: #EFEFEF;
}