update common gray variables

packages/core/scss/bootstrap/theming/_variables.scss

@@ -5,12 +5,12 @@
 
 // Color system
 
-$gray-100: #d2d0ce !default;
-$gray-200: #c9c7c7 !default;
-$gray-300: #bab8b8 !default;
-$gray-400: #adaaaa !default;
-$gray-500: #9a9898 !default;
-$gray-600: #8a8886 !default;
-$gray-700: #585755 !default;
-$gray-800: #323130 !default;
-$gray-900: #171615 !default;
+$gray-100: #f8f9fa !default;
+$gray-200: #e9ecef !default;
+$gray-300: #dee2e6 !default;
+$gray-400: #ced4da !default;
+$gray-500: #adb5bd !default;
+$gray-600: #6c757d !default;
+$gray-700: #495057 !default;
+$gray-800: #343a40 !default;
+$gray-900: #212529 !default;

packages/preset-themes/src/styles/mono-blue.scss

@@ -3,14 +3,14 @@
   @import '@growi/core/scss/bootstrap/theming/variables';
   @import '@growi/core/scss/bootstrap/theming/utils/color-palette';
 
-  $primary: #409cb9;
+  $primary: #439cb9;
   $secondary: $gray-600;
   $highlight: #93e3ea;
 
   @include generate-color-palette('primary', $primary);
   @include generate-color-palette('highlight', $highlight);
 
-  $body-color:                $gray-900;
+  $body-color:                $gray-700;
   $body-bg:                   white;
 
   $body-secondary-color:      rgba($body-color, .75);