better background color for figcaptions

assets/sass/_theme/_utils.sass

@@ -344,13 +344,13 @@
             position: absolute
             right: 0
             top: 0
-            background: $color-background-alt
+            background: $hero-background-color
             text-align: center
             padding: half($spacing0)
             display: block
         p
             @include meta
-            background: $color-background-alt
+            background: $hero-background-color
             display: none
             padding: half($spacing0)
             padding-right: $spacing1