One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,6)(4,5)(7,8)(9,10)(11,18)(12,25)(13,27)(14,19)(15,31)(16,21)(17,23)(20,28)(22,32)(24,33)(26,35)(29,36)(30,40)(34,37)(38,39) involution — undirected(2,5)(3,7)(9,11,14,23)(10,17,19,18)(12,15,24,16)(13,26,28,38)(20,35,27,39)(21,33,31,25)(22,30,37,29)(32,36,34,40)(9,12,16,11,14,24,15,23)(10,18,21,33,19,17,31,25)(13,26,30,22,28,38,29,37)(20,34,36,35,27,32,40,39)(2,5)(6,8)(10,19)(17,18)(20,27)(21,31)(25,33)(32,34)(35,39)(36,40) involution — undirected(1,3,4,7)(2,6,5,8)(9,13,15,29,14,28,16,30)(10,20,31,40,19,27,21,36)(11,22,12,26,23,37,24,38)(17,32,33,35,18,34,25,39)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.