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