One vertex per element, one color per generator, with an edge from x to x·s.
(1,2,4,5)(3,7,8,6)(9,10,12,16)(11,21,24,38)(13,19,27,33)(14,29,23,18)(15,31,28,20)(17,34,32,25)(22,39,30,37)(26,36,40,35)(2,5)(6,7)(10,16)(11,22)(13,23)(14,27)(15,28)(17,35)(18,33)(19,29)(21,37)(24,30)(25,26)(32,36)(34,40)(38,39) involution — undirected(9,11,23,22,15,26,27,34,12,24,14,30,28,40,13,25)(10,17,19,35,20,37,29,38,16,32,33,36,31,39,18,21)(1,3,4,8)(2,6,5,7)(10,16)(17,32)(18,29)(19,33)(20,31)(21,38)(35,36)(37,39)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.