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)(25,26,31,39,30,35,29,34)(27,36,37,32,28,33,38,40)(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)(25,27,30,28)(26,32,35,40)(29,37,31,38)(33,39,36,34)(9,12,14,13)(10,16,17,21)(11,19,20,22)(15,23,18,24)(25,28,30,27)(26,33,35,36)(29,37,31,38)(32,39,40,34)(2,6)(5,7)(9,13,14,12)(10,16,17,21)(11,19,20,22)(15,24,18,23)(25,29,30,31)(26,34,35,39)(27,37,28,38)(32,33,40,36)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.