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