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