category specific icon

i want have icons based in the category. i have two categories “by her” and “by him” so i want have different icons when the posted

this code css changes the icon but the problem is that it is not category specific.below i have paseted the code

.format-box i.fusionicon-pen {
background: url('https://zzuuk.asia/wp-content/uploads/2015/03/10806231_10152420186060666_8494146556852632353_n-12.jpg') no-repeat center center !important;
background-size: contain !important;
}

when i go to "by her" category 

the code comes out is

.archive.category.category-by-her.category-16.logged-in.admin-bar.no-mobile-sticky-header.no-mobile-slidingbar.no-mobile-totop.layout-wide-mode.mobile-menu-design-classic.customize-support.do-animate

whether any one can tell me any the changes need to me made to the css code

thanks in advance ??