using darker color to identify self assessments in grade report UI

apps/openassessment/xblock/static/css/openassessment.css

@@ -1441,7 +1441,7 @@ hr.divider,
           clear: left; } }
     .openassessment .submission__peer-evaluations__questions .answer.self-assessment {
       border-radius: 2px;
-      background: #fdfdfd;
+      background: #f5f6f7;
       padding: 10px 20px; }
   .openassessment .submission__peer-evaluations__questions .answer__source {
     display: block;

apps/openassessment/xblock/static/sass/oa/views/_oa-base.scss

@@ -992,7 +992,7 @@
       // CASE: self assessment
       &.self-assessment {
         border-radius: ($baseline-v/10);
-        background: $color-decorative-quinternary;
+        background: $color-decorative-quaternary;
         padding: ($baseline-v/2) ($baseline-h/2);
       }
     }