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