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