A work in progress dark theme for onedev using Stylus (I am colorblind, so it probably looks terrible. Sorry.)

onedev_dark_wip.css

:root {
  /* Body */
  --headers: #1d1d1e;
  --main-bg-color: #1b1b1c;
  --non-bg-color: #212122;
  --footer: #171717;
  
  --menu-hover: #2b292b;
  
  --modal-bg: #171717;
  
    /* Text Box */
  --text-box-bg-focus:#202020;
  --text-box-bg:#222224;  
    
  /* Issue Board */
  --issue-column:#1a1919;
  /* Code */
  --code-background: #262626;
}

/* -- Main Body ----------------- */
/* ------------------------------ */
.dark-mode .topbar {
  background: var(--headers);
  color: white;
}

html.dark-mode, .dark-mode body {
  background: var(--main-bg-color);
  color: var(--dark-mode-gray);
}

/* -- Cards ----------- */
.dark-mode .card > .card-header {
  background: var(--headers);
  border-bottom-color: var(--dark-mode-light-dark);
}

/* -- Body ------------ */
.card > .card-body {
  background: var(--non-bg-color);
  padding: 2rem 2.25rem;
}

/* -- Floating -------- */
.dark-mode .floating {
  background-color: var(--non-bg-color);
  border: 1px solid var(--dark-mode-light-dark);
  box-shadow: 0 0 30px rgb(0 0 0 / 50%);
}

.dark-mode .floating > .content > .input-assist .help {
  color: #c4bbbb !important;
  border-color: #323248;;
  background-color: #2a2a2d !important;
}

/* -- Text Box ---------- */
.dark-mode .form-control {
  color: var(--dark-mode-light-gray);
  background-color: #1c1c1c;
  border: 1px solid #323248;
}

/* -- Text Box - Focus - */
.dark-mode .form-control:focus {
  background-color: var(--text-box-bg-focus);
  border-color: #474761;
}

.dark-mode .form-control {
  color: var(--dark-mode-light-gray);
  background-color: var(--text-box-bg);
  border: 1px solid #323248;
}

.dark-mode .select2-container .select2-choices .select2-search-field input, .dark-mode .select2-container .select2-choice, .dark-mode .select2-container .select2-choices {
  height: auto;
  background-color: var(--text-box-bg) !important;
}

.dark-mode .select2-drop-auto-width, .dark-mode .select2-drop.select2-drop-above.select2-drop-active {
  border-top-color: #474761;
    background-color: var(--text-box-bg);
}


/* -- Button ------------ */
.btn.btn-primary {
  color: white;
  background-color: #2f2f2f;
  border-color: #323248;
}


/* --| Sidebar ------------------ */
/* ------------------------------ */
.sidebar-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 20px;
  flex: 0 0 var(--topbar-height);
  background: var(--headers);
}

.sidebar-body {
  background: #202020;
  flex-grow: 1;
  height: 100%;
}

.sidebar a:hover, .sidebar a:focus, .sidebar a.open, .sidebar a.active {
  color: #646464 !important;
}

.sidebar-menu .menu-body .menu-link:hover, .sidebar-menu .menu-body .menu-link:focus, .sidebar-menu .menu-body .menu-link.open, .sidebar-menu .menu-body .menu-link.active {
  background-color: var(--menu-hover);
}

/* -- Project Body -------------- */
/* ------------------------------ */
.dark-mode .project-blob {
  background: var(--main-bg-color);
}

/* -- Footer -------------------- */
/* ------------------------------ */
.sidebar-footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0 20px;
  flex: 0 0 var(--topbar-height);
  background:var(--footer);
}

/* -- Side Bar ------------------ */
/* ------------------------------ */
.dark-mode div.side-info {
  border-left: 1px solid var(--dark-mode-light-dark);
  background: var(--non-bg-color);
}

/* -- Modal --------------------- */
/* ------------------------------ */
.dark-mode .markdown-editor > .head {
  background: var( --headers);
  border-color: var(--dark-mode-light-dark);
}

.modal-content {
  pointer-events: auto;
  background-color: var(--modal-bg) !important;
}

/* -- Issue Board --------------- */
/* ------------------------------ */
.dark-mode .issue-boards > .body > .columns > .column > .content {
  border-color: var(--dark-mode-lighter-dark);
  background: var(--issue-column);
}

.dark-mode .issue-boards > .body .board-card {
  background: var(--headers) !important;
  border: 1px solid var(--dark-mode-lighter-dark);
  box-shadow: 0px 0px 4px 2px rgba(0, 0, 0, 0.2);
}

.dark-mode .issue-activities > table > tbody > tr > td.avatar {
  border-left-color: var(--dark-mode-dark);
  background: var(--non-bg-color);
}

.issue-activities > table > tbody > tr > td.content {
  padding-left: 1.25rem;
  background: var(--non-bg-color);
}

/* -- Code Mirror --------------- */
/* ------------------------------ */
.dark-mode .cm-s-eclipse.CodeMirror {
  background: var(--code-background);
  color: #e9e9e9;
}

/* -- Gutter ------- */
.dark-mode .cm-s-eclipse .CodeMirror-gutters {
  background: var(--code-background);
  border-right: 1px solid var(--dark-mode-lighter-dark);
  color: #606366;
}