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