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