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