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