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