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