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