I’m thinking of switching to WriteFreely from GitHub Pages so I’ve been working on a dark mode theme which I thought I would share. There’s a live preview with a sample set of posts at https://write.as/macmhicheil/.
@import url('https://fonts.googleapis.com/css2?family=Lemonada:wght@700');
body{
    background-color: #0D1117;
    color: #f0f0f0;
}
#blog-title a{
    font-family: "Lemonada";
    font-weight: 900;
    font-size: 1.5em;
}
#post #blog-title a, #subpage #blog-title a {
    font-size: 1em;
}
nav#manage ul a{
    color: #56c1bb;
}
#post nav a:not(.home), header nav a{
    color: #56c1bb;
}
#post nav a:not(.home):hover, header nav a:hover{
    color: #347470;
}
body h1 a, body header h2 a {
	 color: #56c1bb;
	}
	
body h1 a:hover, body header h2 a:hover {
	 color: #347470;
	}
header p.description{
    color: #f0f0f0;
}
a{
    color: #56c1bb;
}
a:hover{
    color: #347470;
}
.post-title a {
	 color: #56c1bb;
	}
	
.post-title a:hover {
	 color: #347470;
	}
	
#collection .post-title a {
   color: #56c1bb;
}
#collection .post-title a:hover {
   color: #347470;
}
#collection article p, #subpage article p{
    font-size: 18px;
}
body#collection #wrapper h1, body#subpage #wrapper h1, body#post article h1#title, body#post article h1{
    font-size: 30px;
    color: #f0f0f0;
    font-family: "Lemonada";
}
body#collection #wrapper h2, body#subpage #wrapper h2, body#post article h2#title, body#post article h2{
    font-size: 28px;
    color: #f0f0f0;
    font-family: "Lemonada";
}
body#collection #wrapper h3, body#subpage #wrapper h3, body#post article h3#title, body#post article h3{
    font-size: 26px;
    color: #f0f0f0;
    font-family: "Lemonada";
}
body#collection #wrapper h4, body#subpage #wrapper h4, body#post article h4#title, body#post article h4{
    font-size: 24px;
    color: #f0f0f0;
    font-family: "Lemonada";
}
body#collection #wrapper h5, body#subpage #wrapper h5, body#post article h5#title, body#post article h5{
    font-size: 22px;
    color: #f0f0f0;
    font-family: "Lemonada";
}
body#collection #wrapper h6, body#subpage #wrapper h6, body#post article h6#title, body#post article h6{
    font-size: 20px;
    color: #f0f0f0;
    font-family: "Lemonada";
}
.avatar{
    margin: auto;
    display: block;
    width: 100px;
    height: 100px;
    border-radius: 50%;
}
a.btn.cta, a.btn.gentlecta, a.btn.submit, a.btn[type=submit], button.cta, button.gentlecta, button.submit, button[type=submit], input.cta, input.gentlecta, input.submit, input[type=submit]{
    background: #56c1bb;
    border: 1px solid #56c1bb;
}
a.btn.cta:hover, a.btn.gentlecta:hover, a.btn.submit:hover, a.btn[type=submit]:hover, button.cta:hover, button.gentlecta:hover, button.submit:hover, button[type=submit]:hover, input.cta:hover, input.gentlecta:hover, input.submit:hover, input[type=submit]:hover, select.inputform.cta:hover, select.inputform.gentlecta:hover, select.inputform.submit:hover, select.inputform[type=submit]:hover, textarea.inputform.cta:hover, textarea.inputform.gentlecta:hover, textarea.inputform.submit:hover, textarea.inputform[type=submit]:hover{
    background: #347470;
    border: 1px solid #347470;
}
body footer nav{
    color: #f0f0f0;
}
body footer a.home:link, body footer a.home:visited{
    color: #56c1bb;
}
body footer nav a.home:hover{
    color: #347470;
}
