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)(25,26,31,32)(27,33,28,30)(29,37,39,34)(35,38,36,40)(3,7)(6,8)(10,11)(15,17)(16,18)(23,24)(26,32)(27,28)(34,37)(35,36) involution — undirected(1,2)(3,6)(4,5)(7,8)(25,27,31,28)(26,30,32,33)(29,35,39,36)(34,38,37,40)(1,3)(2,6)(4,7)(5,8)(9,11,14,10)(12,17,20,15)(13,16,22,18)(19,23,21,24)(25,28,31,27)(26,33,32,30)(29,36,39,35)(34,40,37,38)(1,2)(3,6)(4,5)(7,8)(9,12,14,20)(10,15,11,17)(13,21,22,19)(16,24,18,23)(25,29,31,39)(26,34,32,37)(27,35,28,36)(30,38,33,40)(9,13,14,22)(10,16,11,18)(12,19,20,21)(15,23,17,24)(25,30,31,33)(26,27,32,28)(29,38,39,40)(34,35,37,36)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.