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)(19,24)(20,23)(21,22)(25,26)(27,33)(28,36)(29,32)(30,35)(31,38)(34,39)(37,40) involution — undirected(1,2)(3,4)(5,6)(7,8)(9,11,15,18)(10,16,17,12)(13,22,19,20)(14,21,24,23)(25,26,29,32)(27,30,35,33)(28,31,38,36)(34,39,37,40)(2,6)(3,7)(10,17)(11,18)(13,19)(21,23)(25,26,29,32)(27,30,35,33)(28,31,38,36)(34,39,37,40)(3,7)(4,8)(9,12,15,16)(10,18,17,11)(13,23,19,21)(14,20,24,22)(25,27)(26,30)(28,37)(29,35)(31,40)(32,33)(34,38)(36,39)(1,3)(2,4)(5,7)(6,8)(9,13,15,19)(10,14,17,24)(11,20,18,22)(12,21,16,23)(25,26)(27,33)(28,31)(29,32)(30,35)(34,40)(36,38)(37,39)(1,4)(2,3)(5,8)(6,7)(9,14)(10,19)(11,21)(12,22)(13,17)(15,24)(16,20)(18,23)(25,28,29,38)(26,31,32,36)(27,34,35,37)(30,39,33,40)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.