I’ve compiled a list of CSS changes that were necessary to make the transition from the modified Marfa theme I was using to a Dark themed Marfa.

Navigation

Change Background in Navigation to Match Site Background

nav.main-nav {
	background: #3d3c3e;
}

Change Underline and Text Color in Navigation, Footer Navigation, and URLs in Posts

This change depends on your Text Color and Underline Color set by default. If you use the default, you will most likely need to change these to new colors.

nav.main-nav a, #footer a, #post-nav a, p a{
   box-shadow: inset 0 -2px 0 rgba(71, 145, 192, 0.99);
   color: #29ff28
}

Change Author Name Color at the Bottom of a Post Page

#post-meta span.p-author.h-card.dark{
    color: #FFFFFF;
}

Body, Post Page, and Post List Changes

Body

Changes background of site and changes Font Color to White

body {
 color: #FFFFFF;
 background: #3d3c3e;
}

Dates

Underlines and Changes Color of Date

.dates {
  text-decoration: underline;
  color: #FFFFFF;
}

Changes Date Color When Hovered Over

.dates:hover {
    color: #29ff28
}

Headers

Change Header Colors

h1, h2, h3 {
	color: rgba(71, 145, 192, 0.99) !important;
}

Change Header Color on Archive Page

b, strong {
    font-weight: bold !important;
    color: #45b75d !important;
}

Changes Link Text Colors

a {
	text-decoration: none;
	color: #45b75d;
}

Changes the Post Heading Color in the Post List

Source: A big thanks to Simon Woods for the inspiration

#post-list h2 a {
  color: #45b75d;
  text-decoration: underline;
}

Change the color of the post heading in the post list when hovering over.

Source: Again Thanks to Simon Woods this time for making me realize !important was necessary to change the color.

#post-list h2 a:hover {
  color: #29ff28 !important;
  box-shadow: none;
  text-decoration: underline #29ff28;
}

Change the header color on the Post Page

h1.p-name {
    color: #29ff28 !important;
}

Archive Page

Bolds Header in Archive Page

b, strong {
    font-weight: bold !important;
    color: #45b75d !important;
}