Add styles for first day of month.

src/common-components/date-picker/date-picker.vue

@@ -167,6 +167,7 @@
         <div class="grid-item radio-wrapper">
           <input tabindex="0" type="radio" name="day-of-month" id="nov-1" />
           <label class="future-day selectable-day" for="nov-1"><span>1</span></label>
+          <div v-if="isFirstDayOfMonth" class="current-month first-day">OCT</div>
         </div>
         <div class="grid-item radio-wrapper">
           <input tabindex="0" type="radio" name="day-of-month" id="nov-2" />
@@ -332,6 +333,9 @@ export default {
         &:after {
           background-color: $white;
         }
+        + .first-day {
+          color: $white;
+        }
       }
       &:checked + label p,
       &:checked + label span {
@@ -417,6 +421,9 @@ export default {
             color: $white;
           }
         }
+        + .first-day {
+          color: $white;
+        }
       }
 
       + p {