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