The presence (to varying degrees of intensity) or absence of anthocyanin pigmentation within plant tissues (awn, auricle, lemma nerve) is controlled by the genetic locus ANTHOCYANINLESS 2 (ANT2), thought to be encoded by HvbHLH1 (PMID: 21115826).
The following anthocyanin-related traits are scored during national varietal registration trials, as described by UPOV guidelines: "Flagleaf: intensity of anthocyanin colouration of auricles" (UPOV code 4D), "Awns: intensity of anthocyanin colouration of tips" (UPOV code 9D), "Grain: anthocyanin colouration of lemma nerves" (UPOPV code 24). Scores: 1 = absent/very weak, 2 = very weak to weak, 3 = weak, 4 = weak to medium, 5 = medium, 6 = medium to strong, 7 = strong, 8 = strong to very strong, 9 = very strong.
see http://www.upov.int/test_guidelines/en/list.jsp