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