Improve flexibility of applying color to the theme

assets/_scss/_sidebar.scss

@@ -9,7 +9,12 @@
 .sidebar {
   @include clearfix();
   margin-bottom: 1em;
-  color: mix(#fff, $gray, 25%);
+  opacity: 0.75;
+  transition: opacity 0.2s ease-in-out;
+
+  &:hover {
+    opacity: 1;
+  }
 
   @include breakpoint($large) {
     @include span(2 of 12);
@@ -37,14 +42,6 @@
   img {
     width: 100%;
   }
-
-  a {
-    color: mix(#fff, $gray, 25%);
-
-    &:hover {
-      color: $link-color-hover;
-    }
-  }
 }
 
 .sidebar__right {
@@ -73,8 +70,8 @@
 
   @include breakpoint($large) {
     display: block;
-    width: 100%;
-    height: 100%;
+    width: auto;
+    height: auto;
   }
 
   img {