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