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