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