Wow, this one actually turned out pretty well. I was sceptical about the yellow text, but it looks pretty good:

body {background-color: #202020;color: #CCCC00;}
a:link, a:visited, .info_link {color: #404000;}
a:hover {color: #707000;text-decoration: none;}
#headbar, .title, .post .title, .comment .title {border-bottom: thin solid #505050;}
#headbar, input, #description, .info_text, .box, .post, .post .slugline, .post .title, .box .title, .comment, .comment .title a, .comment .title, .header {background-color: #000000; color: #606000;}
.comment .slugline {color: #202000;border-top: thin solid #505050;}
.box, .post, .comment, textarea {border: 2px solid #454545}
input {border: 1px solid transparent;}
input:hover {border: 1px inset #454545}
.page_header .title {border: 0px;}
textarea {background-color: #202020;color:#707000;padding: 5px;}

*Edit* Whoops. I forgot to remove some of my preferences. Take the one above again.

https://addons.mozilla.org/firefox/60/

That is a must have for testing CSS.

I recommend changing text color to #f0e000 and link color to #B0B000

Because it makes it clearer. Right now the text is dark to a dark background, that puts it lighter and makes it easier to read.