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