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