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