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