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