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