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