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