Add light theme root file; add light theme variables file.

services/web/public/stylesheets/app/project-list.less

@@ -170,9 +170,9 @@ ul.folders-menu {
 		> a {
 			background-color: @sidebar-active-bg;
 			font-weight: 700;
-			color: white;
+			color: @sidebar-active-color;
 			.subdued {
-				color: white;
+				color: @sidebar-active-color;
 			}
 		}
 	}

services/web/public/stylesheets/core/_common-variables.less

@@ -857,6 +857,7 @@
 @sidebar-link-color            : #333;
 @sidebar-active-border-radius  : @border-radius-small;
 @sidebar-active-bg             : @link-color;
+@sidebar-active-color          : #FFF;
 @sidebar-hover-bg              : transparent;
 @sidebar-hover-text-decoration : underline;
 

services/web/public/stylesheets/core/ol-light-variables.less

@@ -0,0 +1,68 @@
+// Styleguide colors
+@ol-blue-gray-0 : lighten(#E4E8EE, 6%);
+@ol-blue-gray-1 : lighten(#E4E8EE, 1%);
+@ol-blue-gray-2 : #9DA7B7;
+@ol-blue-gray-3 : #5D6879;
+@ol-blue-gray-4 : #455265;
+@ol-blue-gray-5 : #2C3645;
+@ol-blue-gray-6 : #1E2530;
+
+@ol-green       : #4F9C45;
+@ol-dark-green  : #1C5B26;
+@ol-blue        : #4B7FD1;
+@ol-dark-blue   : #2857A1;
+@ol-red         : #C9453E;
+@ol-dark-red    : #A6312B;
+
+@ol-type-color  : @ol-blue-gray-3;
+
+// Sidebar
+@sidebar-bg                     : @ol-blue-gray-0;
+@sidebar-color                  : @ol-blue-gray-3;
+@sidebar-link-color             : @ol-blue-gray-4;
+@sidebar-active-border-radius   : 0;
+@sidebar-active-bg              : @ol-blue-gray-1;
+@sidebar-active-color           : @ol-blue-gray-4;
+@sidebar-hover-bg               : @ol-blue-gray-1;
+@sidebar-hover-text-decoration  : none;
+@v2-dash-pane-bg                : @ol-blue-gray-4;
+@v2-dash-pane-link-color        : #FFF;
+@v2-dash-pane-btn-bg            : @ol-blue-gray-5;
+@v2-dash-pane-btn-hover-bg      : @ol-blue-gray-6;
+
+// Editor file-tree
+@file-tree-bg                    : @ol-blue-gray-1;
+@file-tree-line-height           : 2.05;
+@file-tree-item-color            : @ol-blue-gray-3;
+@file-tree-item-selected-color   : #FFF;
+@file-tree-item-input-color      : @ol-blue-gray-3;
+@file-tree-item-toggle-color     : @ol-blue-gray-3;
+@file-tree-item-icon-color       : @ol-blue-gray-3;
+@file-tree-item-folder-color     : @ol-blue-gray-3;
+@file-tree-item-hover-bg         : @ol-blue-gray-1;
+@file-tree-item-selected-bg      : @ol-green;
+@file-tree-multiselect-bg        : @ol-blue;
+@file-tree-multiselect-hover-bg  : @ol-dark-blue;
+@file-tree-droppable-bg-color    : tint(@ol-green, 5%);
+
+@content-alt-bg-color            : @ol-blue-gray-1;
+
+// Editor resizers
+@editor-resizer-bg-color         : darken(@ol-blue-gray-1, 5%);
+@editor-resizer-bg-color-dragging: darken(@ol-blue-gray-1, 5%);
+@editor-toggler-bg-color         : darken(@ol-blue-gray-1, 15%);
+@editor-toggler-hover-bg-color   : @ol-green;
+@synctex-controls-z-index        : 6;
+@synctex-controls-padding        : 0;
+@editor-border-color             : @ol-blue-gray-5;
+
+@toolbar-border-color            : darken(@ol-blue-gray-1, 5%);
+@toolbar-alt-bg-color            : darken(@ol-blue-gray-1, 5%);
+@navbar-default-bg               : @ol-blue-gray-4;
+@toolbar-header-bg-color         : @ol-blue-gray-4;
+@toolbar-header-btn-border-color : @ol-blue-gray-3;
+@toolbar-btn-color               : #FFF;
+@toolbar-icon-btn-color          : @ol-blue-gray-3;
+@toolbar-icon-btn-hover-color    : @ol-blue-gray-3;
+@editor-header-logo-background   : url(/img/ol-brand/overleaf-o-white.svg) center / contain no-repeat;
+@pdf-bg                          : @ol-blue-gray-0;

services/web/public/stylesheets/core/ol-variables.less

@@ -140,6 +140,7 @@
 @sidebar-link-color             : #FFF;
 @sidebar-active-border-radius   : 0;
 @sidebar-active-bg              : @ol-blue-gray-6;
+@sidebar-active-color           : #FFF;
 @sidebar-hover-bg               : @ol-blue-gray-4;
 @sidebar-hover-text-decoration  : none;
 @v2-dash-pane-bg                : @ol-blue-gray-4;

services/web/public/stylesheets/ol-light-style.less

@@ -0,0 +1,2 @@
+@import "ol-style.less";
+@import "core/ol-light-variables.less";