visually downplaying step/form instructions

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

@@ -1036,7 +1036,7 @@ hr.divider,
     clear: both; }
 .openassessment .openassessment__steps__step .step__instruction {
   margin-bottom: 20px;
-  color: #3c3c3c; }
+  color: #a5a6aa; }
 .openassessment .openassessment__steps__step .step__content {
   margin-bottom: 20px; }
 .openassessment .openassessment__steps__step .step__actions {
@@ -1512,7 +1512,7 @@ hr.divider,
   color: #aeafb3; }
 .openassessment .submission__feeedback__instructions {
   margin-bottom: 20px;
-  color: #3c3c3c; }
+  color: #a5a6aa; }
 .openassessment .submission__feedback__elements {
   padding: 20px 20px 20px 20px;
   background: #f5f6f7;

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

@@ -176,7 +176,7 @@
     .step__instruction {
       @extend %copy-2;
       margin-bottom: $baseline-v;
-      color: $copy-color;
+      color: $copy-secondary-color;
     }
 
     // step content
@@ -1025,7 +1025,7 @@
   .submission__feeedback__instructions {
     @extend %copy-2;
     margin-bottom: $baseline-v;
-    color: $copy-color;
+    color: $copy-secondary-color;
   }
 
   .submission__feedback__elements {