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