This will render your minos theme ( https://github.com/carsonip/hugo-theme-minos ) in dark colors, just remember to add customCSS = ["dark-minos.min.css"] under [parameters] in your config.toml file. You can use either the scss file and compile it, or directly the .min.css file

dark-minos.min.css

body{background-color:#24292e;color:#eee}#logo,.main-nav-link,a.article-title,p,#page-nav a,.archive-article-title,#main-nav-toggle,.article-entry,.article-toc li a,.tag-cloud a,.article-footer a:hover{color:#eee}a.article-title:hover,a.article-date:hover,a.archive-article-title:hover,#footer a:hover,#page-nav>a:hover,.tag-cloud a:hover,a:hover{border-bottom-color:#eee}.article-entry a{border-bottom:none}.article-entry a:hover{border-bottom:1px dotted #00b6e5}#page-nav .current{background-color:#00b6e5}a,.article-entry a,.article-more-link a,#footer-info a{color:#00b6e5}.article-nav-link-wrap{text-shadow:0 1px #222;color:#00b6e5;text-align:center}.article-nav-link-wrap:hover{color:#eee}#header{background-color:#14191e;border-bottom:1px solid #222}div.highlight,pre,.article-entry code{background-color:#14191e !important;scrollbar-color:#00b6e5 #14191e}.article,.article-date{border-bottom:1px solid #14191e}.archives{border-left:1px solid #14191e}.archive-article-inner:hover{border-left-color:#00b6e5}.article-meta a,.archive-article-date{color:#939393}/*# sourceMappingURL=dark-minos.min.css.map */

dark-minos.min.css.map

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dark-minos.scss

$background: #24292e;
$header: #14191e; 
$text: #eee;
$subtext: #939393;
$highlight: #14191e;
$accent: #00b6e5;


body {
    background-color: $background;
    color: $text;
}

#logo, .main-nav-link, a.article-title, 
p, #page-nav a, .archive-article-title,
#main-nav-toggle, .article-entry,
.article-toc li a, .tag-cloud a,
.article-footer a:hover {
    color: $text;
}

a.article-title:hover, a.article-date:hover,
a.archive-article-title:hover, #footer a:hover,
#page-nav > a:hover, .tag-cloud a:hover,
a:hover {
    border-bottom-color: $text;
}

.article-entry a {
    border-bottom: none;
}

.article-entry a:hover {
    border-bottom: 1px dotted $accent;
}

#page-nav .current {
    background-color: $accent;
}

a, .article-entry a, .article-more-link a, #footer-info a {
    color: $accent;
}

.article-nav-link-wrap {
    text-shadow: 0 1px #222;
    color: $accent;
    text-align: center;
}

.article-nav-link-wrap:hover {
    color: $text;
}

#header {
    background-color: $header;
    border-bottom: 1px solid #222;
}

div.highlight, pre, .article-entry code {
    background-color: $highlight !important;
    scrollbar-color: $accent $highlight;
}

.article, .article-date {
    border-bottom: 1px solid $header;
}

.archives {
    border-left: 1px solid $header;
}

.archive-article-inner:hover {
    border-left-color: $accent;
}

.article-meta a, .archive-article-date {
    color: $subtext;
}