a background color ...

[br4sco]

Ive looked in the style vars and i cant seem to find this certain background color to change it. Why does this even appear ?

[IggyP]

its kind of hard to see....what is that a deleted topic?

[Teascu Dorin]

A link will be better!

L.E. That is a deleted thread. In the style's css_global.css you will find the below code between lines 4854 and 4859:

.topic-list-container .topic-list .topic-item.unapproved {
    background: #E2F0CE;
}
.topic-list-container .topic-list .topic-item.deleted {
    background: #F5E3E2;
}

First is the color for Unnaproved and second for Deleted (this is what you have in your case) !

[TLMD]

Deleted topics have a red background. This is either an unapproved topic or a topic that contains one or more unapproved/deleted replies (= moderated content), thus the triangle icon at the right.

I think you can edit it in the Style Variable Editor ("AdminCP > Styles & Languages > [Your Style] > Style Variable Editor"). There you find two entries: postbit_deleted_background (for deleted topics) and postbit_unapproved_background (for unapproved topics/topics with moderated content).