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