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