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