Bug 1508693: Making help popup use same colours as block config popup

So that the help text can be read in the "Fresh" theme

behatnotneeded: Behat can't tell if colour contrast is bad

Change-Id: I66842fcd7f86bade5a8ed5100a38726d4067d9ea
Signed-off-by: Robert Lyon <robertl@catalyst.net.nz>

htdocs/theme/fresh/static/style/style.css

@@ -853,3 +853,9 @@ ul.searchtab li span.inactive {
 .deletetag {
     background-color: #3e0000;
 }
+
+/******************** Help ********************/
+.contextualHelp {
+    background-color: #10171A;
+    border: 3px solid #000000;
+}