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