package change to reflect modern usage

Author: pahjbo

ObsCore.tex

@@ -1,3 +1,4 @@
+\PassOptionsToPackage{dvipsnames}{xcolor}
 \documentclass[11pt,a4paper]{ivoa}
 \input tthdefs
 \input gitmeta
@@ -35,7 +36,7 @@
 \usepackage{ltablex}
 \usepackage{seqsplit}
 \usepackage{soul}
-\usepackage[dvipsnames]{xcolor}
+\usepackage{xcolor}
 
 %  -mireille- listing params from MIVOT spec
 \lstset{