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