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