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