Gmail theme for Protonmail (https://mail.protonmail.com/appearance)

theme.css

/* Sidebar, logo and topbar background */
.sidebar, #pm_header-desktop, #pm_header-desktop a.logo {
  background: #f1f1f1 !important;
}

/* Invert logo */
.logo img {
  filter: invert(1);
}

/* Default buttons */
.pm_button.primary {
  background: #4688f1 !important;
  border-color: #4688f1 !important;
}

/* Compose button */ 
section.sidebar a.compose {
  background: #d74b3e !important;
  border-color: #d74b3e !important;
}

/* Menu text to black */
ul.menu a, ul.menu i, ul.navigation span, ul.navigation a {
  color: black !important;
}

body section.sidebar div.labels ul li a {
  color: black !important;
}

/* Reload icon */
.sidebar ul.menu li a .fa-repeat {
  color: #ccc !important;
}

/* Blue search thing */
form.searchForm fieldset, form.searchForm fieldset input.query {
  background: #4988ef;
}

/* Top menu active & hover */
header#pm_header-desktop ul.navigation>li.active {
  box-shadow: 0 5px 0 0 #4988ef inset;
}
header#pm_header-desktop ul.navigation>li:hover {
  box-shadow: 0 5px 0 0 #4988ef inset;
}

/* Conversation row */ 
.conversation {
  background: #f4f4f4 !important;
}
.conversation.marked::before {
  background: #CCC;
}
.conversation.active {
  color: #555;
}
.conversation.active h4 {
  color: #555;
}

/* Message */
#conversation-view .message>div.summary, 
#conversation-view .message>div.details,
#conversation-view .message>div.summary .time,
#conversation-view .message>div.summary .status {
  background: #f1f1f1;
}
#conversation-view .message>div.summary .time::after {
  display: none;
}