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)(11,14)(12,16)(13,15)(18,21)(22,24)(25,26)(27,33)(28,36)(29,30)(31,35)(32,37)(34,39)(38,40)(9,11,13,16)(10,14,15,12)(19,23)(22,24)(26,29)(28,37)(31,33)(34,38)(9,11)(10,12)(13,16)(14,15)(17,18)(19,22)(20,21)(23,24)(25,27)(26,31)(28,38)(29,33)(30,35)(32,40)(34,37)(36,39) involution — undirected(1,2)(3,5)(4,6)(7,8)(9,11)(10,12)(13,16)(14,15)(17,19,20,23)(18,22,21,24)(25,28)(26,32)(27,34)(29,36)(30,37)(31,39)(33,40)(35,38)(1,3,4,7)(2,5,6,8)(9,12)(10,11)(13,14)(15,16)(17,18)(19,22)(20,21)(23,24)(25,29,30,26)(27,33,35,31)(28,36,37,32)(34,40,38,39)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.