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