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