Improved text contrast in light theme

src/assets/less/theme.less

@@ -8,6 +8,15 @@
 @import "./app.less";
 
 // Custom OpenFlexure theming
+
+//
+// Colors
+//
+
+@global-color:                                  #666;
+@global-emphasis-color:                         #333;
+@global-muted-color:                            #666;
+
 @global-primary-background: #C32280;
 
 @inverse-primary-muted-color: lighten(@global-primary-background, 15%);