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