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