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