Colour-blind can distinguish colour pallets

Let c: E -> {1,...,k}be an edge colouring of a connected graph G=(V,E). Each vertex v is endowed with a naturally defined pallet under c,understood as the multiset of colours incident with v. If delta(G)>= 2,we obviously (for k large enough) may colour the edges of G so that adjacent vertices are distinguished by their pallets of colours.Suppose then that our coloured graph is examined by a person who is unable to name colours, but perceives if two object placed next to each other are coloured differently. Can we colour G so that this individual can distinguish colour pallets of adjacent vertices? It is proved that if delta(G) is large enough, then it is possible using just colours 1, 2 and 3.This result is sharp and improves all earlier ones.It also constitutes a strengthening of a result by Addario-Berry, Aldred, Dalal and Reed (2005).