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)(11,22)(12,25)(13,31)(14,21)(15,20)(16,19)(17,24)(18,30)(23,39)(26,38)(27,33)(28,36)(29,35)(32,37)(34,40) involution — undirected(1,3,5,4)(2,6,7,8)(9,11)(10,17)(12,26)(13,14)(15,24)(16,32)(18,34)(19,31)(20,22)(21,37)(23,30)(25,33)(27,29)(28,40)(35,38)(36,39)(9,12)(10,18)(11,23)(13,27)(14,30)(15,29)(16,28)(17,33)(19,25)(20,36)(21,35)(22,38)(24,40)(26,32)(31,39)(34,37) involution — undirected(1,4,5,3)(2,6,7,8)(9,13,15,32)(10,17,20,22)(11,14,24,16)(12,27,29,26)(18,33,36,38)(19,31,21,37)(23,30,40,28)(25,39,35,34)(2,7)(6,8)(9,14,15,16)(10,19,20,21)(11,13,24,32)(12,28,29,30)(17,31,22,37)(18,35,36,25)(23,26,40,27)(33,34,38,39)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.