use black instead of grey

cpsievert · cpsievert · commit 8edbac9a3d58 · 2020-05-18T09:41:38.000-05:00
diff --git a/R/scale-hue.r b/R/scale-hue.r
@@ -177,5 +177,5 @@ okabeIto <- c(
   "#0072B2",
   "#D55E00",
   "#CC79A7",
-  "#999999"
+  "black"
 )
