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