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