fix a bug causing issues in tables' cran check
diff --git a/R/util.R b/R/util.R
index 785c6ad..474f352 100644
--- a/R/util.R
+++ b/R/util.R
@@ -110,7 +110,8 @@
     "\\usepackage[normalem]{ulem}",
     "\\usepackage[normalem]{ulem}",
     "\\usepackage[utf8]{inputenc}",
-    "\\usepackage{makecell}"
+    "\\usepackage{makecell}",
+    "\\usepackage{xcolor}"
   ))
 }