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