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