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