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