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