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