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