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