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