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