Update colors for slightly positive and negative (#829)

Author: bjorn3

site/static/perf.css

@@ -87,13 +87,13 @@ img {
   color: red;
 }
 .slightly-positive {
-  color: #ee9090;
+  color: #ea7272;
 }
 .negative {
   color: green;
 }
 .slightly-negative {
-  color: #90ee90;
+  color: #74b374
 }
 .neutral {
   color: black;