docs: add colors

README.md

@@ -23,6 +23,8 @@ The full palette is available in RGB, HTML or CYMK conventions.
 must always be present in your system (or at least in the project directory)
 before trying to use the other packages.
 
+![](screenshots/colors.png)
+
 ### ULiege-trigon
 
 This package customizes the [Trigon theme for Beamer][trigon-repo] in order to