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